Terrible Bug

I was editing a sign and doing very sensitive work on pixel art with the smallest circle brush which only draws one pixel at a time.
I was working and working and editing this sign, but little did I know I had network problems about to hit.
There was a lag spike, I was disconnected from the server and lo and behold, when I rejoined I lost two hours of work on a sign.
It had defaulted back to a previously sketch-only state and looked like ass, I had almost finished and it was in full colour by the time I was booted and, to make it worse, the sign had locked.
Locked for no reason and left me unable to edit it any further.

Can anyone advise on this? Is it possible to have this bug unlock the sign? I only ask because my friend can edit it.

I have lost my work and it is a loss to me that I cannot do what I love in this game.

This has happened to me before, so I am hesitant to play again.