Dion Berryman's try was enough to cancel out Hamish Watson's score for Edinburgh, and Carlo Canna outscored Nathan Fowles, Sam Hidalgo-Clyne and Kinghorn from the tee.
And despite being thrilled with the opportunity to run out in an Edinburgh jersey for the first time, Scotland under-18 international Kinghorn admits the disappointment from the defeat was more important.
"It felt great to run onto that pitch with the Edinburgh shirt on. It's something I've wanted to do for a very long time and I'm just glad that my chance came," he told Edinburgh Rugby TV.
"It was a frustrating result for us though. It's hard for the boys when sometimes the game just doesn't go your way, and that was one of them.
"We came close to getting the bonus point on that last play, and when it came off the boot I thought it was looping over but it just fell short.
"It's very frustrating for the lads but we've got a week to pick ourselves up, and everyone wants to get straight back out there and show what we can do because that definitely wasn't a top performance by us.
"We know that we can be a lot better so I think the lads will come in and work really hard this week and hopefully we'll get a result over in Ireland at Connacht."
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