The Temple Open House was not to be a missionary event and all of us who served there were carefully instructed to not proselyte. All guests were invited to complete a Comment Card and IF they asked for more information by missionaries (by checking an appropriate box on the bottom of the card) then the referral could be processed and forwarded to missionaries. There were 166 visitors who asked for more information.
But as I went through the thousands of Comment Cards, I found that quite a few had shared sacred experiences felt during their visit. Many were powerful. We received permission to glean the cards with the strongest comments. Those with phone numbers were given to the sister missionaries to call as a follow-up to their Open House visit. Of the 333 called, 83 of them (25%) said they would like to have a visit by the missionaries.
One of our sister missionaries left a message on an answering machine and the called person called back. Sister Brown was just leaving the Call Center when the call came in. When Sister Brown offered to have missionaries visit the caller, the lady asked if the missionaries could come that evening. Sister Brown tracked down the elders assigned to the lady's area and they said "yes" they could. Later that night, after the visit the elders called Sister Brown and reported that they had taught the lady the Plan of Salvation and she committed to be baptized in February! How Great is That!
Another 160 Comment Cards had no phone number but left an e-mail address. I sent each one a personal e-mail message and referred them to Mormon.org and the "I'm a Mormon" video interviews. I don't expect any responses but feel that many (perhaps another 25%) will take the time to learn more.