I tried starting the campaign again, but it didn't help, which is logical – the weapon has already been obtained and is no longer on the map, and it cannot be given to Anastasia because she won't join the dynasty until the end of the campaign.
Lastly, when replaying the map, I couldn't use the "Restoration" spell (it was always unavailable). I had to rely solely on its mass-effect counterpart. The situation is the same on the next map; it seems this bug will persist throughout the campaign.