I've seen it happen before. They don't "count" as part of any alliance so they won't get aoe buffs like protect or medica 2 but they can still roll on loot that drops to their correct party. They'll never get replaced by queue in progress DF'ers because the alliance is technically full. In all, it's a bug but not a terribly serious one. Just toss them a regen every now and then to make sure they don't die.

Also, OP was not particularly bad at grammar...