I was golfing at Rutgers Bay Lake Course near Aitkin, MN. Playing by myself just a week ago. The leaves were scattered everywhere, falling from the trees after they changed their colors. It was a nice 45degrees out and I was all bundled up. I was shooting alright then on hole 14 these two older men asked me to join them. I excitedly accepted and played with them for the rest of the round. I bogeyed hole 14 on a long par 5 after my tee-shot went out of bounds. Coming up to hole 15, playing about 145yd from the blue tees, pin was middle-back of the green. The green is a little elevated and you cannot actually see the hole as a sand trap is blocking it. The green formed a nice little bowl that played well if you could hit it there. I looked in my bag and grabbed my 9-iron thinking I could hit it higher and it would hit nicely. I did not tee the golf ball (using a Titleist DT Wound 90 ball) just let it sit on the cold, wet grass in the tee-box. I hit a nice stroke that was off-target towards the right trees. All of sudden my ball rolled down from the right slope, pin-high, with some serious speed. I looked over at one of the gentleman and said "Did that go in?", he said I'm not sure but it was pin-high. I thought since it had so much speed it either had to hit the cup perfectly and go in or it rolled off the other side of the green that had an even nastier slope down towards the water. I hopped in my cart and drove to the green, got out of the cart did not see my ball anywhere so I thought it rolled off the other side. Grabbed my chipping wedge and my putter and thought I hope I can save Par here. Then I thought, well I might as well check the hole and I could not believe my eyes. The ball was in the cup. I was so excited and in utter disbelief. Grabbed my ball out of the hole and high-fived the other two guys. Holy Crap!! My first ACE!! Not even thinking about it I tee'd off the next hole with the same ball, I was 1 foot away from going out of bounds. The other two guys were like you gotta put that ball away!!! I grabbed it and replaced it with another ball, whew, that was close! Proceeded to bogey the next 3 holes and still was in complete shock. That's my story, cheers!