Sussex Police confirmed officers were called to Smiley's Cafe in South Farm Road in the early hours of Thursday, January 13.
They were responding to reports of a break-in.
"A till was reported stolen but was returned after being found by a member of the public," a police spokesperson said.
"An investigation is ongoing."
Smiley's Cafe posted about the incident on Facebook.
Staff said the till had 'little money in it' when it was stolen.
Anybody who witnessed the incident, or has any information that could help with the investigation, is asked to contact police online or by calling 101, quoting serial 0158 of 13/01.