Never bought my own handtruck
Backpay for dishonesty? Good luck with that.Cover your ass.
You note that the sup did this before so he or she would likely do it again, sadly your next.
Get the shop steward and BA involved and ensure they are aware that this Sup does this and has history. They should have fun with them. You’ll be back with backpay if you do things right and don’t have other issues.