Can P2SH-aware nodes permanently lock bitcoin?

I've been around here for a bit, but I wanted to get a solid grasp on the technical side of bitcoin before diving into other areas. This question is kinda tough for me, and I'd appreciate some clarity. So, the standard script for a lightning network HTLC output has this conditional branch that needs a user to know the preimage of a hash. Plus, it needs a valid signature. But it got me thinking: what if, back in the early days before P2SH existed, someone made a locking script that accidentally fit the P2SH model? Let's say they only meant to set up a lock that said "the spender needs to know this hash preimage". The thing is, that preimage isn't a bitcoin script, so it can't be executed even if it fits the P2SH structure. Do nodes that recognize P2SH end up locking this bitcoin forever?

Yes. If the top stack item which has to be interpreted as a script (the redeem script to be exact) is not a valid script for any reason, that output is unspendable forever because according to the consensus rules the transaction spending it would be invalid.