Kakanui Community Catchment Project co-ordinator Nicola Holmes said she was "incredulous'' when she heard of the theft.
"You've got to be joking. Unbelievable,'' she said. "It's for the community, but it was also created by the community. That's the bit that really rankles me.''
There were "at least'' 120 people involved in creating the sign showing the 850sqkm catchment's boundary and the environmental and recreational opportunities in the area.
The bolts which attached the 820mm by 1120mm map to the galvanised steel structure had been removed and the sign taken.
"Hopefully, there will be some sort of shaming process that goes into returning it - we want it returned,'' she said.
The signs were sponsored, and the largely government funded project, which focused on improving water quality, reducing soil erosion and increasing biodiversity in the Kakanui River, was "budgeted down to the last bit'' and there was no money to replace the $500 sign.
The sign was installed on Tuesday. Pupils of Kakanui School unveiled it on Thursday, and it was apparently taken on Friday or Saturday night.
The sign was the first of four to be unveiled in the Kakanui River catchment. One would be unveiled at Clifton Falls today.
Signs were also planned for the Alps 2 Ocean cycle way in Enfield and at Gemmells Crossing reserve.
