Thanks for the replies. I searched everywhere for a black lite...Petco, Pet Smart and lots of little places and none carried them. That's why I was happy when I saw it came with the Urine Gone!
I'll surely try the peripheral theory tonight.

My 'sniffer' works every time, though
LOL! I haven't resorted to getting on all fours for a snoot full. The smell sticks in my throat for hours when I've happend upon it unintentionally! Do you rent out your sniffer? Care to come to my house and assist? LOL