Okay so I remember reading this fic a while ago set post-avengers with the assumption that Phil had died. The fic was set on a Captain America internet forum that Phil had basically created and a lot of the fic deals with the other members of the forum, Phil's long time friends, trying to find out what happened to him after he vanishes from the forum.
His friends don't know that he works for SHIELD, if I remember rightly. And in the end they find out that he died so a load of them decide to hold a memorial for Phil at his grave and Steve and a ton of SHIELD agents show up.
I recall it making me want to bawl EVEN THOUGH I categorically knew that Phil was going to come back.
I might have read it on ao3 but I'm not certain.
If anyone could help me out, I'd really appreciate it! :)