So I was on a maintenance call for a building. A string of 3 plugs were off and it's a huge building and I couldn't locate the breaker after 2 hours searching. I went with the building owner inspecting every single panel and gfci plug to test if that was the issue. We couldn't locate the breaker or power source for those plugs. So I gave up looking for the breaker and did the following instead. There was a baseboard heater on a 20 amp circuit nearby. I tapped off one of the hots from that circuit with a 12/2 wire rated for 20 amps. There is no neutral so I left one wire capped off in that box. The other end I replaced with a 20 amp receptacle. I took off the hot wire I identified as the home run wire going to the panel and replaced it with the hot wire I spliced from one of the hots of the baseboard. I kept the neutral wire from the home run cable as I needed that neutral to complete the circuit. So now all the plugs work.
Just wondering if there is any fire issues or nuisance tripping this will cause down the line? It's been 2 months and the client hasn't called to complain.