Nothing will happen to the process server ... since your case was dismissed (and that's the best outcome for lack of process) you obtained the relief already.
You may have a civil case of conspiracy to tamper with evidence ... check your state case law to check. But the process server may just have made a mistake & you won't win the case.
Also, you got a "document in the mail that a process served served you"??? Who sent you such a letter? It may be the process server served someone else at your address, which is OK to do.
Best action for you to take is nothing.

