Can a wallet get encrypted by default?

Hi there, does anyone know if a wallet can get encrypted without the owner entering a passphrase?
I have a wallet .dat file from 2013 that I’ve restored (with litecoin core/qt) , and I specifically did not initially set up a passphrase or encrypt the wallet.
When I restore it, I can see the coins, but it’s now encrypted, and asks me for a passphrase to transfer coins. I’m wondering if there is another wallet software, or something else I can open the wallet with- or how this could even happen. Maybe the later versions encrypt everything?
Any help would be much appreciated,

Thanks heaps

Jono

There’s no chance that a wallet can be encrypted without you knowing it. It’s most likely that you setup wallet encryption later on and just forgot.