Here are instructions as posted by a fine feller named EletricDawn a week ago or so:

Your local cloud save folder is here:
C:\Program Files (x86)\Steam\userdata\YOURSTEAMID\892970\remote

Enter the "worlds" folder and look for a file called something like "YOURWORLD.db.old".

WARNING: The following steps only work, if you have NOT logged in since your death:
0. Quit Steam. Make especially sure Steam is NOT running!
1. Create a copy of the entire "remote" folder and put it somewhere safe. It is highly recommended to backup this folder periodically (and to have multiple older copies) so you can fall back on them if for some reason Steam Cloud/Valheim go crazy and reset your world to day 1.
2. Enter the "worlds" folder and move the file "YOURWORLD.db" and "YOURWORLD.fwl" out of there and put them on your desktop for now.
3. Remove the ".old" from the files "YOURWORLD.db.old" and "YOURWORLD.fwl.old"
4. Get back into Valheim and give it a try.
5. If you got your boar back, then you can delete the files from step 2. They are no longer necessary to keep.

As usual, should any of your IM forces be caught or killed, this agency will disavow any knowledge of your actions.
I hope this helps and good luck, Mr.Phelps.