as a former landlord, i can tell you that they ( landlords) can NOT enter a residence without giving the tenant a minimum of 24 hours notice, and if they do, it is considered by the law as BREAKING AND ENTERING/BURGLARY. if the grow was totally legal, your cousin needs to call the sheriff and report what happened, and that the landlord broke in, and stole your shit ( if they entered the house without permission and if they removed items from the house without permission, thats a felony bro)

id be on the phone with the sheriffs office pronto and report it, then get alawyer to sue the bitch in court