I wonder how to politely handle the following situation as a PhD student. Any suggestion will be appreciated. Thanks in advance for any help you could provide.
I was working for almost one year in modelling some results on the work of another PhD student visiting us. He is supposed to be first author.
After a very hard and intensive work I got some positive results and we realized that part of his data was wrongly interpreted or wrong.
That student left time ago and returned to his home country and I sent him the results in order he could prepare a first draft. Aftersome times with no answers I wrote him again asking for the status of the draft but he had stopped because he was close to defend his thesis.
He became a doctor , continued in his lab, and I sent him the results again, as suggested by my supervisors.
After many times of asking him for a draft along several months he sent a document with many figures and almost no text or explanations. I've been kindly asking him to fill it with some information in order to work on something. However he has done anything for longer than 3 months. I feel he is not interested in publishing it anymore. He is always answering 'I will send you something'but no answers.
This work has been extending for almost 2 years already. Other co-authors and supervisors are tired of the situation but they seem not to care about. I have talked about this with the coauthors but not evolution has been observed. I am frustrated as it is been delayed so long and It is not my paper but my work. I am really worried.