I've actually had this happen to me for a job I needed a LOR for years ago. When asking for a letter, I
always say the obligatory, "Would you be willing to review me
positively for this position.." and he had accepted. I was also under the assumption we were on good terms; I had recently been invited to his house with the rest of our research group for a celebration. For what turned out to be reasons political, this person wrote a poor letter and suggested another student in my cohort the position. The recruiter stopped taking my calls and never responded to my e-mails. The PI who wrote the letter even pretended to be sympathetic when I spoke to him about how I hadn't heard from them.
The other student hadn't even applied yet, nor was aware of the opportunity -- but was working in the position shortly after. I was friends with the student who landed the job and he told me off hand how he received the position, unknowing that I had reached for it first.
Since then I have a similar paranoia as the OP, but I learned how to trust again!
I learnt a lot from the experience too. I, before that experience, had been pretty unaware exactly how political academia can be. Thank goodness this was before I applied for the DVM program!
I'm sure a lot of people have similar stories...[/QUOTE
Omg. That is horrible... I'd be mortified :/