Shirley Kelly (77), Maggie King (68) and Lyn Jordan (66) had been using The Joy of Sex as a prop in the latest Fortune Theatre production, Dirty Dusting.
"It was a hard cover copy, too, with illustrations," Ms King said yesterday.
"We just hope that whoever took it is enjoying it and we'd like it back as soon as they're finished with it," Ms Kelly said.
"But, really, why would anyone take an essential prop from a play?"The theft was discovered just minutes before the Tuesday night performance of Dirty Dusting.
"It was in a drawer of a desk on stage.
Only people who have been to the play would even know it was there," Ms Kelly said.
However, with the play attracting full houses in its first week, the suspect list already numbers in the hundreds.
Stage manager Liz Webster quickly mocked up a copy of the book for the Tuesday night show.
The A4-sized copy of Dr Comfort's The Joy of Sex is one of the main props in Dirty Dusting, which is a comedy about three elderly cleaners who strike it rich when they accidentally intercept a phone call to a telephone sex line.
Fortune Theatre staff are also upset about the theft.
"All we know is that it was taken from the main stage of the theatre between Sunday night and Tuesday," marketing assistant Louise Moulin said yesterday.
"But, if whoever took the book would please return it, preferably in a plain brown paper bag, then no questions will be asked."
Dirty Dusting continues at the Fortune Theatre - sex book or no sex book - until July 26.
