"He actually sent me an emoji [because] he didn't think I was gonna respond and that's why he got really casual, but it was sweet," Hightower told US Magazine.
Warner is preparing to enter his fifth NFL season. The 49ers made him a third-round draft pick in 2018, and he signed a five-year extension worth up to $95 million before last season.
Warner recorded a career-high and team-leading 137 tackles, seven tackles for a loss, three quarterback hits, four passes defensed, one forced fumble, and 0.5 sacks last season, per Pro Football Reference.
More San Francisco 49ers News
49ers' Fred Warner addresses Armstead's departure, Greenlaw's recovery, Super Bowl window Trent Taylor snatches up 49ers star receiver's old number Anthony "Spice" Adams to announce 49ers' draft picks in 2nd and 3rd rounds George Kittle's message to Brandon Aiyuk amid contract talks with 49ers: "Be patient"