It's Not Americas Home Place Without Tyvec Wrap

I returned from my business trip two months later to see siding being put on the house. We just happened to take a drive one day to see progress on the new house and the siding sub-contractor was placing the vinyl siding on the house. As the standard Americas Home Place house does not include Tyvec house wrap, we asked the project manager to have the house 'wrapped' before the siding was installed. We wrote out a check, passed it to the project manager and told everything was taken care of and the tyvec would be put on the house.

Lucky we were passing by that day as we noticed 1/3 the house was sided, but the tyvec wrap was not applied. We mentioned the missing tyvec to the sub-contractor and he said he had forgotten about the wrap, it was in the truck and he would take care of it... What does the reader think? "Did he forget the wrap or was he intentionally skipping a step when Americas Home Place project manager was not around to make sure the work was being performed?"
We assumed that forgetting the tyvec wrap was an honest mistake.