If your friend's server is his local computer (and not an actual dedicated server), he could use devcommands and spawn in your gear. Else, you can start a new temporary world and use devcommands and spawn in your gear. But if you meant a magical way to retrieve it, probably not.

Your character files are stored in "%appdata%\..\LocalLow\IronGate\Valheim\characters". Locate the "charactername.fch" file (whatever your character name is), rename it "character.bak". (This step is just so you have a backup.)

After that, rename the "charactername.fch.old" file to "charactername.fch" and log in again.

If this does not work, then you'll probably have to try the devcommands. (Rename the files to what they were before you modified them.)