I've only used Electrum and this has never happened to me but isn't it possible to recover the wallet even without the .dat file as long as you have the passphrase?
Not likely... A wallet.dat from 2011-2012 is probably generated by bitcoin core. Electrum was first released in 2011, but since core was the dominant wallet at that time, and wallet.dat is the default filename of a wallet generated by bitcoin core, it's probably a bitcoin core wallet.
At that time, bitcoin core was not an HD wallet, each time you funded an address, a new random private key was generated and saved in the wallet.dat, no seed phrase, no xprv, just random private keys stored in a wallet file.
@OP: did you make a backup copy, as suggested by a previous poster?
If so, i'd probably recommand you to re-try pywallet, but maybe fetch an older release from around the time you created the wallet? A different option might be to download an older bitcoin core version, install it on an OFFLINE pc and dump your private keys?