My CEL flashed once while driving a few nights ago but didn't come back

[EddieSVX]

My CEL flashed at my while crusing during decceleration a few nights ago. It quickly went away and never came back. I decided to check for engine codes today and it displays a code 28 (Knock sensor 2, LH), no other codes.

Could the knock sensor be going bad, did something random trigger the knock sensor, or could there be any other issues? Is the CEL supposed to stay on if it's a bad sensor? My engine wasn't running rough and did not feel powerless. It also idled normally.

I may be buying the pair of knock sensors from one of the guys selling them in the for sale forum, but before I do, should I just clear the code and see what happens in the next few days?