Mole Gets Lost(1997)
(The first book in the Willows in Winter series)
A Picture Book by William Horwood
When Mole fears for his friend Ratty's safety, he intrepidly sets off into the dark and wintry night, intent on rescue. However, Rat's safe and sound and it's Mole who has put himself in danger. A search party is established, but the friends despair on finding Mole's Will. All except Ratty.
Used availability for William Horwood's Mole Gets Lost