I'm not sure what happened as I didn't notice that it went missing untill the next time I was going to use it, but after searching for solutions for a bit, I noticed other people having similar issues. It seems like the tool you are currently holding can be consumed together with the stardrop when you get it from your wife. I tried going forward a few days, as I heard that tools should get sent in the mail if they are missing, but it didnt work. That could be because I have other hoes (unupgraded) lying around in other huts, as I played a bit multiplayer before. I'll probably just use one of them, since it seems like the only option I have, but it's a bit sad having to use so much money to upgrade it again. Just sharing this so that it hopefully gets fixed in the future.