Just for some context, last night I was called out for a hot water tank leak at one of the buildings I service. When I got there, I found it was a leak on the hot water side pipe, which was out of my scope, so we had to call a plumber to come and fix it. Long story short, I was there for 4 hours as I waited for the plumber to repair the pipe. He had to run back and forth for parts because certain places were out of stock, hence why it took so long. My time was filled by waiting, watching, and being on my phone. This morning, I was talking to the lead engineer and he told me that he wouldn't have done that and found more work to do while waiting. He also stated he wasn't saying I SHOULDN'T have done it, but it's just not what he would have done.
Basically I'm wondering if I was being lazy and should have done something else with my time? My thought process at the time was that I was only there for the call, other wise I would have been home. I feel like I'm over thinking it, but I can't decide either way on whether I was wrong or right. On one end I feel justified in my reasoning, as any extra work could have also got done today, but on another side, I feel guilty. So reddit, did I screw up? Any and all advice/criticism is welcome!