The decision was "tough", said Cremer, whose spin bowling had the hosts in early trouble on the final day before a 121-run partnership between Dickwella and Asela Gunaratne secured Sri Lanka's best-ever run chase of 388.
Dickwella rescued Sri Lanka from a precarious 203-5, but the left-handed batsman's gritty 81 needed plenty of luck.
The wicketkeeper-batsman survived a stumping from Sikandar Raza's off-spin on 37 and was then dropped by wicketkeeper Regis Chakabva on 63.
The stumping reprieve cost Zimbabwe dearly. It was referred to Indian third umpire Chettithody Shamshuddin, who ruled him not out despite replays showing his toe was on the crease — a case where the batsman can be given out.
"From what I saw, I honestly didn't see any doubt why it should be not out, but it's just one of those things," Cremer, who led his side to victory in the one-day series, told reporters.
"I suppose you have technology and it clearly shows ... it's tough when those things go against you when you are trying to win a Test match on the last day," said Cremer who took four for 150.
Left-arm spinner Sean Williams finally got Dickwella caught behind but his prolonged stay was key in the hosts' victory.
Gunaratne (80) put on an unbeaten 67-run partnership with Dilruwan Perera (29) to dash Zimbabwe's hopes of a first Test win over Sri Lanka.
"We tried hard. We have missed a few opportunities, but I am very proud about the way the guys played," said Cremer, who got nine wickets in the match including his maiden five-wicket haul in Sri Lanka's first innings.
"To win the ODI series and to push them in the Test match taking it to the last day was a very good effort from the boys."
Chettithody Shamshuddingraeme cremerniroshan dickwellaregis chakabvaSean Williamssikandar razaSri Lanka vs Zimbabwe 2017
First Published: July 19, 2017, 10:13 AM IST