Congratulations Vacman. You have the only cache that has been detained for drug possession, incarcerated, had mug shots taken, and then released on its own recognizance to its guardian without any duty to return.
To be honest if this had happened to my cache, I'm just twisted enough that I would have played it for whatever I could. I probably would have edited the cache record to indicate the location had moved to the Palos Verdes Estates Police Department evidence room, and explain the way to access the cache is to enter the Police Department and ask for it. If they are wily enough to get the property clerk to bring it to them (unlikely), then kudos for them (take a picture of the cache as proof). If they are able to add to the log book, then they could be serious grifters if they had a mind to. If they are able to remove something from the box and add something else, then they should be considered super-geocachers. When done, they should tell the property clerk to return the cache to the evidence room so others can request it in the future.
On a serious note, I'd make sure that all traces of the so called offending substance are removed before re-hiding the cache. It doesn't take much in the way of smell for someone to get in trouble if the history of the cache is not known by local authorities.