This happened to me when I replaced it with an LED. The bulb is back in there now and has not fallen out. I am interested to see what people suggest.

I've had a few loose GI bulbs on Sterns before that I ended up using some tac putty to keep to stay. I think it's called tac putty at least, it's that stuff you get to put up posters when you can't use tacs in the walls, it's kind of like silly putty. I just put a very small bit in the middle of the socket, put the bulb in and it holds like glue.

On WH2O the bulb in front of bigfoot gets broken all the time (at least until you add another post to stop that from happening...).

I'd use a real shop vac and vacuum the entire playfield, then stand the playfield up on end and vac everything that falls in the cab. Pound it gently a few times to shake any other glass chips loose.

Glass is abrasive, it's worth the time to get it all out.

If the socket does not have gripping power anymore, it is time to replace it.