Probability of Bed bugs from library - HELP :)

I am in court tomorrow with my landlord. I am representing myself and the landlords lawyer is trying to say I got bed bugs from the library. I contacted the library and they emailed me this. The library has 1.49 million visitors each year. It is 160,000 sq feet of space and has 231,000 items you can check out. They have had 17 bed bug hits from a sniffer dog but when investigated they found no bed bugs.

Since they found no bed bugs I would assume the probability of getting them from the library is zero. Is this correct?

If I consider the 17 bed bug hits as possible outcomes then do I divide 17 by (the number of items times the number of visitors)? 17/(1.49million x 231,000)?