Mr Bishop was particularly disappointed because the association was now down to one backstop net to share between the junior and senior groups, just as games were starting back up.
The net is not the kind of equipment you can just buy at a sporting goods store. Due to their size, the nets have to be specially made and would cost about $1000 to replace.
"We've only just started out, that's the sad thing about it. Replacing the net would really set us back in funds," Mr Bishop said. "I guess people could break it down for fencing, or try and flog off the metal poles for scrap. But that'd be foolish to do locally.
"All our members, as well as friends and family, are keeping an ear to the ground in case it turns up somewhere," he said.
Rotorua police Sergeant Mike Membery said it was unusual for sports equipment of that size to be stolen, and the theft likely required a bit of planning. He said it would be difficult for the thieves to sell it as scrap metal.
"Scrap metal dealers are required to take photo identification and other details of everyone who sells them scrap. They're quite good at asking questions and reporting suspicious sales."
Mr Bishop said whoever took the net could just return it to the park, no questions asked.
If you have any information contact Rotorua police on (07) 348 0099, or Central Bay Softball through its Facebook page.