Little Sheltie is scared and needs help getting home

I have a missing Sheltie - actually in Hunt county, but in case he makes his way up into Fannin County, I'm trying to get the word out everywhere I can. I was actually dog sitting so I don't have a photo. I had only had the animal 24 hours. I was working on a farm in Celeste, and after four hours of staying close by, one of the sheltie's I'm watching took off. He's medium size, if I had to guess, about 35 pounds. He has a dark face and dark fur down his back, but otherwise looks like Lassie. He answers to the name of Rennie, but he is shy and skittish. He was last spotted on 1089 in Hunt County Saturday night 10:30pm (I was there and called him but he wouldn't even come to me - he took off into the darkness). If anyone thinks they may have spotted him or found him, I can be contacted at librariansunshine@yahoo.com or 903-813-2559. Thanks.