normal Patch Kit "glue" is NOT Glue.. it softens the rubber allowing the Patch to VULCANIZE to the tube.... the patch and tube blend together.

Allowing it to "dry" for a few minutes gives the chemicals time to soften the tube material to a workable depth.

if the patch fails, you'll note that it began peeling away at the edges.....
your saving grace was letting the patch set up over a longer time...
a trailside rush job would eventually fail, and the tube might even become vulcanized to the tire.. not that I'VE ever done that...

i test patched tubes in water... usually the restroom sink.
Trailside? i use the "wet lips" test before re-installing the tubes... air up the tube, lick your lips, then pass the suspect areas past your wet lips... you'll FEEL the leaks, if any.