Hello it certainly works for me on my install testing that search string and the only place the PI#233849 is entered is the title of the photo.
Are any of your photos simple titled that? I think not
Your title's have this -PI#233849- not PI#233849 hense it can't be found since none of the words in the title are like that.
I bet if you uploaded a photo with PI#233849 in the title as one of the words it would work