All-in Rules Question

[magic_man]

The other night in a 6-12 home game, a player lost a big pot and was almost out of chips. He got up to smoke a cigarette and missed his blinds, and then came back a couple hands later, but only had $8 left and didn't seem like he was interested in rebuying. The dealer asked if he wanted to come in and he said "Sure, what the hell," and threw the last of his chips in.

Since he missed his blind, he has to post $3 dead plus the big blind, but since he doesn't have enough to cover it, how does it work? Does he post $2 dead and a full big blind, or $3 dead and all-in for $5 blind? Has anyone ever actually seen this happen? Thanks for your help.

~Magic_Man