I recently found myself in a frustrating situation at work. I was asked to quickly learn the specifics of a position from a colleague who was leaving, as she was the only one with that knowledge. I stepped up and handled her responsibilities along with my own during her two-week transition period. When the position opened up, I interviewed for it since it was a slight promotion and I was already familiar with most of the job details. However, the role was given to someone else, and now I’m being asked to train this new hire from scratch. To add to my frustration, I haven't received any compensation for the extra work I took on or for the training I’m expected to provide. I'm contemplating whether I should ask for compensation before agreeing to train this new employee. I’m looking for advice on how to approach this situation and whether it’s reasonable to request something in return for my efforts.