Lennon was struck by the £1 coin in the dying seconds of the first Edinburgh derby of the season, which finished 0-0 after Hibs were reduced to ten men.
Hearts thought they had a winner in injury time, but Dikamona’s goal was ruled out, causing Lennon to turn and gesture towards the fans seated in the main stand.
Seconds later, he crumpled to the ground after the object hit him.
He got slowly to his feet and grabbed his face while he was attended to by colleagues and match officials.
It was the second ugly incident involving the crowd in the match - with a Hibs fan appearing to strike Hearts goalkeeper Zdenek Zlamal, who hit the deck after the confrontation.
Earlier, Florian Kambieri was sent off for a second bookable offence after clashing with Hearts’ Oliver Bozanic.