I got to an out-of-town job years ago and couldn't find the power cable to Tyros. Went to Radio Shack and got one. After I got back of course I found the other one.
Dean M and I got to another job about 50 miles away and I had forgotten the keyboard! I cranked up the laptop and sang with midi files while he played along on fiddle and electric piano. They loved it. I actually did the same thing at a local NH job and rather than go home and get the kb, I used the laptop. They didn't care. They just want to hear music!
You always have to have a backup in place for everything just in case nature, senility, stupidity, etc., decides to kick in.