If it works it works. I was just referencing in case there was more to be done or if someone else is thinking of doing the same thing.
Basically if two components are compatible you can go over one with the other without sanding before the first is completely dry / cured.
If the first is cured you should always have some sort of mechanical bond ( sanding ).
Very true, but if he applied it in his Garage, and didn't use a heat lamp, he more than likely only got it to "low-flash" cure(2-6hrs, depending on outside/shop temps)("High-Flash" is generally 20mins-3hrs, when baked or heated). Depending on his outside Temps when sprayed and allowed to cure, it would take awhile if the temp and humidity was low.
If it was "Low-Flash" Cured, chances are good that it would still be able to bond, but you also run into the possibility of any excessively covered area sagging(running). Now if it was "High-Flash" Cured, and the Epoxy wasn't sanded before applying the bed liner, it will easily chip and flake with the slightest heavy contact. Any exposed Epoxy, will soak up moisture like a sponge, and would hold it to the metal(Like Bare Plastic filler(bondo)/DP Primers are notorious for..)...