How to reroute a circuit that goes through a return air plenum
Is that acceptable for new construction?  No.
Does anything compel you to fix it now? No.

I'd check very carefully that the insulation on the black &amp; white wires is unaffected (sounds like it is).  Then slip something over to mechanically protect those wires.  A stiff bit of plastic sheet rolled up and slipped through the joist should do it.

Then caulk the hole for airflow purposes, and consider replacing the entire return plenum: there is no caulk and it leaks air.  At best you're getting basement air into the plenum because the pressure is lower.