Does a PC who was KO’d earn experience for that combat?

A friend of mine’s character just died, and as we chatted he lamented all the bad luck he had over the course of the campaign. One thing that stuck out (other than his death being at the hands of a rather careless player character) was that he said his DM didnt give him XP for fights where he got knocked out.

As a DM of 5th edition this seemed odd, so I chimed in with “Thats a pretty harsh house rule.” and then my friend explained that his DM is extremely anal about playing RAW.

So I petition the collective knowledge of RPG Stack, I have scoured the PHB and the DMG about XP gain, and the rules about being KO’d and I have found nothing that says a character gets no XP for a fight if they are knocked out, am I missing anything? Is it possibly a rule added in one of the supplements?