Is it possible that report in Report Builder can be deleted by itself ? (ELM 7.0.2 iFix009)

That seems highly unlikely. I have never heard of any other customers reporting such behavior. More likely is that user or some other user deleted the report. I have no idea what Power BI is, so cannot comment. Before submitting a defect, the submitter needs to provide some factual evidence of the issue, and ideally, steps to reproduce it. A defect that has neither factual evidence nor provides some means for development to reproduce is likely to just be closed as "cannot reproduce" as there is nothing that development can use for investigation. I suggest you look at rs.log covering the period 28th Jan to 8th Feb to see if there is anything that seems relevant. If there is, then contact IBM Rational technical support.