Tinyblu, you always refer to your boyfriend's potential other partners as "toys". Do you understand that if he's really poly, he might be pursuing real relationships with other women--like, serious ones? Poly people don't just have "escapades" with outside partners. I hope this has been explained to you.
I am confused about your situation. If this woman is just a co-worker who's come back from mat leave, why is she emailing you and chat requesting you? Do you have something to do with his job?
You admit that you over-reacted, but still say that being contacted by "one of his toys" is unacceptable to you. Why?