You won't be able to smoke anything it has come in contact with. Washed or not. It's beyond horrible. My concern is that it may telegraph through the plant to a degree. I also did a little more research on melting point. It's about 1700 deg. F for silver so it depends on the flame source for us. Butane lighters can get to around 3500 deg F while a hemp wick likely falls bellow the 1700 deg mark. I can't find a real temp for one though.
Silver is a Noble Metal so it's not toxic like a Heavy Metal. Regardless, too much of anything is usually not good so I would not make a continual practice of smoking treated plants whether it can be tasted or not. I like the idea of solo cups. I've more or less moved all my breeding and seeding projects to small pots for less waste in the end. With early treatments and S1 seeds on the same plant it renders it useless for anything but edibles. This will be my normal approach from now on. Late treatments will likely be kept in reserve for emergency measures. I feel safer whether it is or not