Michael Bell is at a loss to explain Margot Did's no-show in the Palace House Stakes on Saturday, after the Nunthorpe winner scoped clean after the race.
Last year's York heroine ran with some credit in defeat on her first couple of outings this year in Dubai, but was a well-beaten last of 16 on her return to the track at Headquarters.
Bell must now aim to get Margot Did back on song for next month's King's Stand Stakes at Royal Ascot.
"We've done all the tests on her - we've scoped her and had her bloods done, and nothing has come to light," said the Newmarket handler.
"I think we'll just have to put it down as a bad day at the office and we'll try to get her back on song for the King's Stand at Royal Ascot."