If it was plugged it wouldn't flow any water. It sounds like it currently flows cold water.
Yes I have seen this with single lever faucets that allow some cold water to mix with the hot. Also some have an adjustable mix limiter (anti-scald) which could be set wrong.Not always, I had one caked a couple of years ago, that let cold in but not enough hot so it always felt cold. Another thing that I have seen minerals do, is stop the Diverter valve from working properly in the faucet, when you spend over 2 decades living off mineral laden well water, you will see all kinds of weird things happen LOL