There are a dozen basic things he could have done in order to ensure that he wasn't stiffed. Off the top of my head:
- Visiting the offices meeting the team, including those people specifically assigned to his project
- Requesting staged payments so he pays as phases are met and not prior to receiving any deliverables
- Checking the contract to ensure there's no mention of outsourcing. Did he even check the contract at all?
- Getting references from former customers to ensure the validity of any claims made by the development firm
- Searching online for feedback and reviews about the firm
- Just asking questions in general. "Where is my app going to be developed and who by?" seems like an obvious one before you spend nearly a hundred thousand dollars
Edit: Looking at your post history you seem to be associated with a software development company. Did you not speak with your friend about his decision to spend an extraordinary amount on a development project ahead of him getting in this mess?