This!It's just business.
Nothing to worry about at all. We are all disposable assets at the end of the day.
If there's a gig I can't play I'll always say to the rest of the guys to get a dep and they're exactly the same and I've helped to find my own dep. You don't stop the rest of the band earning good money if you're busy, but we're totally cool like that.
If it's an original gig that's a completely different thing and ignore everything I've said. I'd want to know what was going on.
Either way a simple "OK, if you can't do the gig we're going to get a dep in because...XYZ" would have been the cool thing to do.