Little bear is very bad

I don't know what to do about this. Little bear was 'that way out'. I had to go three rounds just to get him dressed this morning, although he could have been worse, he could have been better. At nursery he made a massive breakthrough with the potty training, but got told off for snatching three times and had his good behaviour sticker taken off him. Coming out of nursery he ran right behind a car about to reverse - I couldn't grab him quick enough! I should have known there was trouble ahead but it is literally only yards from the nursery to our house.

About half way along there are some steps going up the hill at the side of a row of houses built into the hill. The hill is really steep and the steps are like stairs. Little bear decided he wanted to go up them, it was a short cut. I sighed deeply as he started up them and called him down, normally no problem. He didn't come down. What was worse, he dived behind the row of houses, so was out of my sight.

I was petrified. I have never had him out of my sight before. I caught up with him at the back of the houses, but he shot off again. It's only a little snicket, and he belted along and was obviously disappointed to reach the end and find that it didn't come out where he thought it would. So he decided to go down the steep grassed slope the other side of the row of houses. At this point I was almost in tears - I couldn't follow. The slope is extremely steep, slippy and uneven. Little bear reached the bottom without any bother but I didn't dare attempt it. All I could do was look helplessly at my four year old standing on his own next to a very busy main road.

I yelled at him to stay where he was and belted along the back of the houses, down the steps, and along the front of the houses. I suppose the row of houses were about 100 yards long. Little bear had gone. He had gone back up the hill. I just stood there - I had left my mobile at home as well so I couldn't call darling father to come and stand at one part of the loop while I chased little bear. Fortunately little bear decided to reappear and come back down the hill. He was crying and said he was very worried for me. I suppose he thought it terrifying when he went to find his mum, and I wasn't where he thought I would be.

I think I got through to him that it was a bad idea. I tried to explain how dangerous it was, and I think I got through when I said that a big dog could have bitten him and I wouldn't have been there to help him. But he wasn't really taking it in.

He managed to run off just about a year ago, but at least he was in line of sight all the time. Now I am at my wit's end wondering what do I do now. I have told him if he behaves like a baby he can go back in reins, but I am not really planning to do that. Besides, this is practically unheard of. But I can't take the risk of it being a regular thing.