Completely possible. The seal on hearing protection needs to be uniform and sufficiently tight. It doesn’t take but a couple of those kinds of high energy sound impacts to cause lasting effects.
Maybe we've been lucky, but when we lived in Colorado before, the gun/rifle case was in the large dining room (that we never used). Right next to the front door. Then, when we lived in Jacksonville, the case was in a closet. Actually, there was a couple of times there, that we left our front door unlocked. One time, we were gone for over two hours. Nothing missing. Where we are now, there's not enough closet space for it to go into. However, it is in our spare bedroom. But, I'm sure not going to be like my 1/2 brother who keeps his handgun fully loaded, no locks and in the nightstand next to where he sleeps. Definitely not us!
Decided this morning to buy my wife electronic (battery operated) ear protection to wear in the indoor range. It's pretty loud in the room and the cheap ear protection she currently wears just isn't enough. Bought her one like I have. Due to going to an outdoor range and wearing cheap non-electronic ear protection, I now have to wear hearing aids. Our 9mm is very loud when shot and she can barely hear me if/when I talk to her.