Mary, Denbury Resources bought out Encore. Denbury now operates most of the production along the Cedar Creek Anticline (See Fallon County for more info). I don’t know if they’re actively leasing outside of that formation, though a call never hurts. The other companies in that area are probably better prospects for current leasing. Just to clarify things, you’re looking for the companies in that area not all of those in MT.
The State’s website is cumbersome and I don’t know that I can explain it, but it sounds like you’re figuring it out. Perhaps try the State’s map. Zero in on your area and then you can click on nearby wells. The best I can say is play with it for awhile.
As to the lack of websites, also search for phone numbers and physical addresses. On occasion I’ve had good results by simply sending a letter. It does not matter how you reach them, you just want to learn if they have an interest. Good Luck.