I'd be hurt and feel sad for a while, but I know mine well enough to know that he'd tell me if he found out first, and I wouldn't just throw him out if I did. I can't imagine circumstances that would make me leave over that issue alone. Life is terribly short.
I got a taste of how short it can be, for several harrowing hours, when my partner recently had a heart attack while hiking in a nearby park. His cell phone died on the way to the hospital, neither the paramedics nor the ER contacted me, and I wasn't able to track him down until the next day (with help from his brother back East, but that's another story). I was sure he was dead, and uncertain if I'd even see his body. Every deadly scenario ran through my head: carjacking, mugging, highway hit-and-run... But, after desperately, crazily, scouring the streets of L.A. for his car and phoning everyone I knew all night and into the morning, I found out he was alive and in a nearby intensive care unit. That kind of experience tends to put things in perspective, and let me discover what was truly important to me.