I just had an invisible creeper blow up on me.
I was building another room to my mountaintop home. And then I hear the sssssssss sound of a creeper. It exploded and I took damage. However, there my house was still intact, not a single block destroyed (my house is wooden). I looked through my entire house but there was NOTHING. I have NEVER had anything spawn in my house, my house is almost floating near the top of the map, so nothing can get in.
I've had Zombies spawn before that were invisible. I couldn't attack him and he couldn't attack me though, and I'm 100% certain that he simply wasn't above or below me. The sound would follow me around and you'd even hear the appropriate type of footsteps as he moved on gravel/dirt.
I guess Creeper spawns are possible, but since they explode they can probably attack you unlike those other mobs.
were you near water? if you were, then the creeper could have fallen in, thus acting like tnt in water, i have tested this. it explodes, and it only does the shockwave damage, not the destroying blocks part.