So it was a very small transaction, sending from a BlueWallet on-chain address to a Phoenix on-chain address for splice-in.
Completely forgot to include the screenshot in my original note, but got the error pictured below. When I tried to cancel the transaction instead speeding it up via RBF, that worked for whatever reason.
So I’m just out a few hundred sats, but ended up getting the funds where they needed to go.
Thanks for the explanation on CPFP, I guess I’ve never used that before - just RBF. 