Premature resignation

After a poor result in their first game, Colchester A have won four matches in a row. The most recent match was a 3-1 away win against Witham A to move them up to 2nd place in Division 1. Svein was first to finish, while he was definitely winning was his opponent's resignation premature?

[Event "NECL League div 1"] [Site "?"] [Date "2016.01.06"] [Round "?"] [White "Kjenner, Svein"] [Black "Pearce, Dave"] [Result "1-0"] [ECO "B11"] [SetUp "1"] [FEN "r2qr1k1/1b2bppp/1p3n2/p1pp4/2P5/2BQ1N2/PPB2PPP/3R1RK1 w - - 0 19"] [PlyCount "1"] [EventDate "2015.??.??"] {This game ended fairly quickly. After} 19. Bxf6 {Black resigned. Some commented that it was premature. I also had that feeling, even though I knew Black position should be lost. But there is still room for mistakes...} ({After } 19. Bxf6 Bxf6 (19... gxf6 $4 {is mate in two with} 20. Qxh7+ Kf8 21. Qh8#) 20. Qxh7+ Kf8 21. Rfe1 {[%csl Rb7][%cal Re1e8] Black has difficult problems. Important is the Bishop on b7, allowing the following variations: If} Rxe1+ { my plan was} (21... g6 22. Bxg6 fxg6 (22... Rxe1+ 23. Rxe1 fxg6 24. Qxb7 $18) 23. Qxb7 {White is winning. But I think Black should have continued the fight.} ) 22. Rxe1 g6 23. Bxg6 ({According to the machine} 23. Ng5 {was better. The Knight can of course not be taken. The engineline goes} Bg7 24. Nxf7 Kxf7 25. Bxg6+ Kf8 26. Re5 $1 {it would have been fun to play this move, but I am afraid I would not ever even consider these lines. That is more for engines and postal players.} Bc8 27. Re8+ Qxe8 28. Bxe8) 23... fxg6 24. Qxb7 $18 { If Black tries} dxc4 {White can play} 25. Re6 {with the idea} Qd1+ 26. Ne1 Bxb2 $4 27. Qe7+ Kg8 28. Rxg6+ Kh8 29. Qh4+) 1-0