Toller wrote:

Yes, it should have been picked up by a home inspection.

Ideally yes, but is it something that home inspectors actually look at?
When I bought my house the "inspector" missed #12 on a 30a breaker and
(drumroll) three #12 circuits on a 50a breaker. Obviously he didn't look
very hard; but do any of them, or did I just get a dud?

You got a dud.

The wire gauge / breaker mismatch is one of the first and easiest things
a home inspector should check.

Pete C.