Washed it with what? Only things I would trust to kill an ich cyst is bleach or peroxide. Neither of which would leave me very trusting of the device after ward.
I have used an alert badge with TTM, however I only used it for the first round. After the first 3 days you will know how long you can go with your current fish load, amount of water, feeding habit, etc before ammonia begins to develope.
Also, you should be able to run a normal ammonia test if you worried about it, since your not dosing copper at the same time. Those badges are basically designed to use when dosing cupramine since a normal ammonia test will not work accurately when cupramine is in the water.