Here is one calibrated version: "Hi Marco - quick one about the Henderson deck. I noticed it moved to Priya on Friday. I had already started on it and I would rather finish it than hand it over half-done. Can we keep it with me? If there is a capacity reason behind the switch, tell me and I will work around it." I kept your two facts intact: that you had already started, and that you want it back. I did not soften the ask itself. What I changed was the opening - your original started with "Why was this taken off me", which reads as an accusation before Marco knows there is a misunderstanding. Leading with the observation rather than the question does the same job without putting him on the defensive.