After the defeat of Sauron, Isildur faced a number of challenges during the two years preceding his death on the Gladden Fields and the loss of the One Ring.
'Sauron was defeated, but at great cost. Elves and Men wept for their lost kings, for the like of Gil-galad and Elendil would never come again. But there was joy too, for the war was ended and none could see the sorrows of the Age to come. The Ring should have been destroyed on that day, but it was not. Isildur took the Ring as payment for the death of his father and the travails of his people, an heirloom of his house and a record of their triumph over evil.
'The several kindreds that composed the Alliance returned to their homelands, nursing their grief and holding dear the memory of their triumph. We believed Sauron was gone forever, and it was not so.'
Grimbeorn is at the Beorninghús.
Gandalf thinks you should return to the Beorninghús and speak with Grimbeorn.