Possession of weed for personal use is legal. However, selling weed is a crime at both state and federal levels.
So some clever fellows start a psychic weed finding business. Call them up, describe the weed you've lost, give them a credit card number, and if their psychics are able to locate your lost weed, they will deliver it to you.
ETA: Source: https://wjbq.com/psychics-in-portland-are-helping-mainers-find-their-lost-weed/