The artist is calling on the trade to contact the police if they are offered the picture.
Fruitsellers, West Africa was painted c.2014 and purchased from Whitewall Galleries in Guildford.
Pratt said: “Obviously this is distressing for the owners and we want it back.”
But he added jokingly: “Naturally I’m hoping it’s a sign my work’s improving! Like all older painters my work is more sought after now. Possibly speculation of value increase when I ‘pop off’!
Pratt is represented by gallery Clarendon Fine Art and is hosting a private view at the Kings Road, Chelsea, gallery on November 7.
Anyone with information about the stolen picture should call the police on 101 quoting Surrey police crime reference number 45190091415.