Mercenary died, then disappeared.

I did a few t17 maps, merc died a couple times in them. Hates the abomination boss when it's juiced I guess. Decided to do a fortress, went in, forgot to revive my merc from before, went back to hideout only to find my merc is gone entirely. I couldn't have hired anyone over him, I had an extra slot and I didn't hire anyone new. I didn't release him, as he was alive, then dead, then apparently gone.