BB, to check a rear plug, drop the socket into the plug well, and then follow it up with an extension or two. Ten just latch onto the extension with your socket wrench and turn until the socket mates up with the plug. If you try to put the wrench with the extension with the socket in all at once, there is no way it will work.
It took me 2 tries to get me rear plugs out. Once you know how to do it, it's a snap.
BTW, I had the same problem with a plug that came out. Turn out, the threads in the head had oil on them, so I just wiped the threads clean and re-installed the plug. Bingo, no more problem.
