It's unfair (to me) that what he did for a living was used against him and assumed that he must have faked the phone call. So if he was a plumber, the entire case would be different. There would have been other suspects and leads followed because they would have considered the phone call as proof she was alive at that time.
Someone brought up a good point a while back. Even the best expert would have been taking a risk doing this because no one knows all the different trails that are left behind, router logs, computer logs, timing, phone records, etc. It would have been very risky.