From the GM end, having a non-committed player is frustrating and I think you just have to roll with it for your sanity. I had a player that was calling in to cancel last minute seemingly all the time for much less important reasons than having recently had a child! I just got to the point where I planned gaming without him and if he showed up it was a bonus. Kind of like having an active NPC in the party!

From the player end, our group plays on Mondays. My job changed for four months where I worked every other Monday. So I could only attend 50% (or less) of our gaming sessions! I told our GM to count me out, but when I was able to show up I either played some one-shot NPC for the evening or just enjoyed being at the table with friends. And honestly, I had one or two pretty memorable NPCs that were supposed to be one-shots, but ended up becoming larger pieces to the campaign puzzle! So that is an option for your player too if they’re inclined.

And as for being shy, I HEAR YOU! I am the same way. I’m fortunate that many in my current gaming group aren’t. I will warn you of one thing though. If you stick with people that aren’t providing your gaming needs because you’re too afraid to venture out, then you’re going to be unhappy as a gamer. I wasted WAAAYYYY to much gaming time playing with people I had marginal fun playing with because I was too afraid to go out and try new things. All I can say is, try to embrace change. Just try playing with a few different groups at a hobby store or convention once or twice. I almost guarantee you’ll have fun and meet some new gamers to boot!
Samuel Van Der Wall recently posted…Review of Neon Sanctum

I have a situation where we are now down to 4 players due to a baby being born and one of the players that is left is really ‘responsible’ and ‘corporate in their direction with work’ and only sees the game sessions as a tertiary thing he enjoys or allows himself to enjoy, and I can understand that, but from my perspective I put in time to to do this thing and run it… if you interested enough to play in my mind, you are interested enough to make time to regularly attend… we meet once a month, and if I don’t aggressively schedule times ahead he is always choosing 1-1/2 or 2 months out instead to attend

That in my mind detracts from everyone elses experience since they are capable and willing to attend more. While having said that, he encourages us to play without him when it’s not convenient enough for him… ok, well, that means we are down to 3 players. I haven’t missed one game session so far since started Phandelver in July… I would hope that would be the case with the players also.

So, have said all that, can you either marry in both the different directions that running a session can provide based on different number of players. Also, since we meet at one of the players houses (a couple) since they have a bigger place for all us to play and room for my stuff, I am a bit shy on trying to invite new (strangers) into their home and haven’t given much thought to add players through a ‘looking for group in RL not online’ except to think it’s a bad idea right now.

Visual aides can assit you in this a great deal. Recently I had a situation where two of the characters were involved in a short break-away infiltrating a building. I handed the other players a map of the village and the tunnels beneath the village to help them in their plan to liberate the captives being held beneath the grange. They planned out their next moves while listening to the action the others were engaged in. Worked out nicely.

I think this might be a great topic for an article…
John Lewis recently posted…Review of Neon Sanctum

For example, if our Drow Rogue sneaks away from the party and gets into a little spotlight time with a side adventure, I’ll typically talk to the other players about what our next plan of attack is. When John gets back to us, I (or another player) usually catch him up to speed and say something like the following:

“John, while you were dealing with Melissa’s (Drow Rogue) adventure, our characters have been talking in the inn. We’ve believe that those coins our characters were given are actually cursed and being used to track our movements. So we’ve decided to go spread them around the Citadel. Stacey threw his coin in a fountain, Colin sold his to a merchant, Vance gave his to a homeless person, and I just threw mine in the gutter.”

Usually John will say, that’s great. And we move forward from there. Occasionally, one of those actions will provoke something from an NPC or something else and John will narrate it out. In this example, Stacey, Vance, and I just succeeded at our actions. But John chose to roleplay Colin’s action out a little more since the merchant was wary why this person was selling a collectible coin given to him by a noble at a bargain price.

Hopefully that gives you an idea on how it works at our gaming table!
Samuel Van Der Wall recently posted…Top 5 Reasons for Player-Facing Mechanics