I guess that's one way to learn the hard way
ha ha. Even with Tripple Seven that isn't too corosive, NEVER put your breech plug in without grease. (or you'll have what you had just happen)
Heck even when I bought my brand new inline, the first thing I did was take the breech plug out and grease it more than the factory had it before the first shot.
(I've had the pleasure of helping someone who didn't grease his breech plug once).... That experience was enough to make sure I put a little extra on each time I clean my gun!!
I'd make it a habit of greasing the plug on every cleaning.
If you didn't on this go around after you got it out and cleaned it, I'd take the time to take the plug back out and grease it before you resight in, otherwise you'll be in the same boat again.