If it was a set up you need to be very careful going forward.
They have already shown that they will lie. You need to question anything that seems out of the ordinary and communicate via DIAD texts that you take pics of.
You may end up seeing a lot of strange mis-sorts/ mislabeled packages.
Always text asking for direction.
Take 5-10 min break and check your load at the end of the day for pkgs planted by management.
Take pics of your load after completing your deliveries.
Do not cover any mistakes, admit to them and no lies.
You have to be squeaky clean and watch your back since they have shown dishonesty.