I'm very sorry to hear this, I highly suggest you to contact an art moderator to know what happened and what caused this deletion. Here you can find the list of all moderators, scroll down and you will find the list of art moderators:
https://www.newgrounds.com/wiki/help-information/site-moderation
MchectorII
Did you receive any notifications from M-bot?
Roboman142
No I didn’t, and that’s worse, I didn’t not receive any notification that my artwork was deleted via email.