Sorry about your troubles RW.
The past is the past, but something that could help in the future is to zip-tie a small zip-lock bag onto the handle of the sprayer. When you mix up a "potion", write up a note (what the potion is, date you mixed it, date you will use up or discard it).
I have a special sprayer for herbicides. It is sold by Round Up, therefore has their logo printed on it. I'll never accidentally use that sprayer for pest contol.