What does clover see molly doing?

Clover accused Mollie of allowing one of Mr. Pilkington's men to stroke her nose. Later.....

"A thought struck Clover. Without saying anything to the others, she went to Mollie's stall and turned over the straw with her hoof. Hidden under the straw was a little pile of lump sugar and several bunches of ribbon of different colours."

"Three days later Mollie disappeared."