Mineral property still owned

I have mineral rights in richland co mt in 2005 i owned 11.85185 net mineral acres on a 320 acre lot now in june of 2005 i sold 6 of those acres and was sent a check from a McCartney Petroleum Inc based out of sidney mt I acknowledge i did get one ck from them and did indeed sell that 6 acres but they are saying now and in fact sent me their deed paperwork that i did sign selling my remaining 5.85185 acres now here is the part that is confusing I did get the first ck but the second ck i never got i moved i know with the first one it came certified mail and they are supposed to keep records and well as i should have I have contacted Mr McCartney who is now retired and sold his company to another oil company and explained the situation he looked through his records and only had a tracking # for one of the cks yes he said he sent out both of them but i only recieved one my question is how do you go back to 2005 and find this info out to verify that indeed you did not recieve the 2nd ck due to my moving i believe i never signed for it and there for shouldnt i still own the mineral rights to that section twn22N range59E section27w1/2 I am going to contact a lawyer tom because i know i never signed or got the second ck Thank you for any input Theresa Hennnen