Kendall Jenner had a strong indication of who Gerry Turner had the hots for on “The Golden Bachelor” before everyone else … based on what she saw on his cell phone at dinner.

Gerry was over at Kris Jenner‘s house early on during the ‘Golden Bachelor’ season when Kendall saw something she shouldn’t have — which was shown in a recent teaser for “The Kardashians” … and now, TMZ knows what it is Kendall discovered.

Gerry tells TMZ … Kris invited him over for dinner because Kendall is a big fan of his and the Jenners were calling his daughter Angie on his phone when they discovered a very telling saved contact … a photo, name and number for Theresa Nist, the woman Gerry popped the question to on the show.

‘Golden Bachelor’ was only a few episodes into the season when Gerry’s secret was out, he says … but Kris and Kendall kept it close to the vest and didn’t spill the beans, even though they knew who he would propose to on the finale … long before it aired on TV.

Gerry says the cat was out of the bag within 5 minutes of meeting Kris and Kendall … he says a conversation about reality TV quickly turned to Kris and Kendall commandeering his phone to call Angie, who is a huge fan of the Kardashians … and that’s when the Jenners stumbled on Theresa’s contact info.

Don’t get it twisted, Gerry doesn’t feel like the Jenners were super intrusive … he says they were inclusive, gracious, warm, friendly and elegant. Their dinner party included a ‘GB’ episode in Kris’ theater room and he tells us the whole night was amazing.