Oh I had that happen a few times when I had my AR-15. That led to hours of cursing on my hands and knees. Wish they would have giving me some sort of warning. Guess that's what I get for not reading the instructions all the wayI was hoping there was a good story about you taking it apart and then having the spring and pins go "to the winds" - I've had to comb through the carpet to find that tiny pin from the bolt before, no fun.
Thats why I usually do it in the tub with the shower curtain pulled... You have one fire off in to oblivion once and you learn your lesson...