Fundraisers at Stella Maris in Ramsey are requesting the return of a flag and banner.
The thieves stole the Manx flag and a donated Yamaha banner possibly along with other items from the site last night (Thursday).
Organising marshals say around 100 people are at the big grandstands at Stella Maris and they would like the items back.
They say there's been a great spirit as they raise money for the Greyhound League Isle of Man and the thoughtless action marred what was an otherwise enjoyable day.
Chief minister proposes issuing new MiCards to those who can't open bank accounts
Timeline for new CRHS 'a bit tight', says education minister
More details about MiCard replacement could be revealed today
New scheme hopes to help autistic adults on the IOM find their place in society
Residents 'must make voices heard' on new Ramsey Harbour flood defence proposals