evap system is incredibly tempermental, any little tiny leak or crack in a tank seal or vacuum tube will cause the light and be intermittent till it gets worse

If the DTC comes back, and you must replace the cap, then you can get the OE one for around 15.00 plus shipping.
ACDelco GT279 is the one that is OE and tethered.

I had the same code for two years. It was the cause for many headaches. I have a scanner so I kept clearing it hoping I fixed it. After some time I found it was popping on as soon as my gas got to 3/4 tank. I tested the theory for many weeks and the result was consistent, soon as the needle hit 3/4 the light glowed. Since I already replaced the gas cap, first thing anyone does when an evap code pops, I decided to test the tank and filler neck. I hooked up my fog machine and ran a tube into the filler neck. Turns out there was a tiny pinhole in the filler neck.