I believe if bitcoin is sent to an address that is with a correct checksum that particular bitcoin isn’t lost because there is tendency of it been spent
A PKH address is a ripe160 hash of a sha256 hash of a pubkey, with a one-byte prefix and a 4-byte checksum suffix
But a hash is irreversible, so there's no way to know whether any arbitrary 160-bit string was created from a pubkey. And it is trivial to make a random 160-bit string appear to be a Bitcoin address - prepend the prefix, calculate the checksum and append it. For example ...
x'FF000000000000000000000000000000000000FF' is 1QFKJvAyJ1EBHtYqxZd1Wq2TCDPQY7UqMD
The checksum x'BA873B0C' is valid, which means by your definition, it's spendable
The only validly lost bitcoin is that sent to a burn address, like using the the usual OP-return method which means the output can never be spent, this is the only way the coin is lost in my opinion
Correction. An OP_RETURN TXO does not have an address, so it's not "sent to a burn address"