Most of the time that customs sieze a package with a "personal use" quantity of gear, they will just confiscate it and its the end of it.
However, I wouldn't take any chances with illegal class 3 substances, and I would make sure my house was good to go in the event of a search.
I would think if they were going to do a search, they wouldn't tell you that your gear got seized until they arrived at your doorstep. That would give you too much time and opportunity to make sure your house was clean