What reasons did Peter have for disregarding the possibility that the conspirators would realize that one of their documents had been stolen?

From the text:

There was probably no danger, for, in the welter of papers on the yellow gentleman’s table, the absence of the play script might go unnoticed for some time, long enough for him to feel uncertain when and where he had mislaid it. It looked, too, as though he might have finished with it — the twenty-six copies of the sonnet had evidently been made — and in that case the yellow gentleman would not trouble himself unduly.