Sorry, I was under the impression it was the same principle. If it didn't happen, or you weren't there, then it didn't happen/you weren't there. You can't claim you were there retroactively, no matter how much you may want to. Sometimes IRL gets in the way (A lot of times, actually) and that's agitating. I know, I'm in the same position. But for those instances your character will simply have been unavailable/incapacitated. Maybe you would have helped. Maybe you wanted to. At the end of the day though, the character wasn't there.
I'd say if a character wasn't there and claims to have been IC, then others who were there would be completely in the right for calling them out for being a liar. Cos that's what that is, lying. Lying about participating in something that you did not participate in.