Welcome to the forums. What I would suggest is to call the Wyoming DOW and see if they have a record of when it may of been. I would suppose that it would be about the same time that they started regular hunting seasons in the state.
Try to put your tree stand in a tree with plenty of background cover, keep the prevailing winds for that time of the year to your face, and take care of those pesky squeaks and creaks your stand may have developed while sitting in the shed. A good treestand lube can be made by heating petroleum jelly until it reaches a liquid form. Some hunters have reported success by including a cover scent in this mixture before applying it to their stands.