"I believe", is a creative way of saying, "I don't know, for sure", or, "I'd be lying if I said: 'Yes, Reg Andres DID sign the Report'."

Since interested parties had requested engineer-signed copies ---days earlier--- to no avail, it appears Mr. Hewett would have known, for certain, whether the Report was signed, or not.

That seems to leave us with only the latter explanation!