If you really lost/messed your contacts when trying to delete your phone log you sure botched something.

The phone log is stored in /home/nemo/.local/share/commhistory/commhistory.db
The contacts in /home/nemo/.local/share/system/privileged/Contacts/qtcontacts-sqlite/contacts.db

It's 2 completely different databases, you just cannot change contacts when you modify commhistory.

(but if you'd said you deleted your SMS'es accidentally, well, that would be possible. Messages and phone calls are both in same database...)