I'm afraid I didn't and was a wuss. I have always struggled with being assertive, especially with people I don't know and feel I may have both let my ds down and set him a bad example.
This is what happened. We were in the playground and ds's inflatable football must have blown out of the buggy without us noticing. Ds was on the climbing thing (he is 3) and I was helping des2 (11mths) to play on the slide.
A woman got talking to me and then we realised that her ds had my ds's football and ds was was saying, 'It's mine,' and the other boy was saying ,'No it isn't.' Realising what must have happened, I said something like, 'Oh it must have blown out of the buggy, it really is ds's but, ds, it would be fun to play with this little boy.' Basically, my hope was that she would get her son to relinquish his hold but that we would encourage them to play together with it as my ds enjoys this but doesn't get much chance as I don't have friends with children the same age.
The other mother said weakly, 'Give it back, ds,' but when he totally ignored her she just shrugged and giggled at me and resumed talking. I was not that into her conversation and, in any case always keep half an eye on ds just in case. What followed was her ds (he was a year older than mine btw) held onto the ball and my ds chased after him, saying 'It's mine!' and her ds kept denying it! It doesn't sound that bad but ds kept looking at me as if to say, 'Why don't you tell her!' I don't know, he just seemed bemused, not upset, but a bit wtf. At one point they stopped running and her ds pushed mine, enough to make him stumble. She said something like, 'Don't push,' (weakly) Again, my ds looked more bemused than upset and I didn't want to look over- protective so I said nothing and the running resumed. She said to me, 'He's harmless really!' and gigggled again; I thought, 'He may be when he's 4 but he won't be at 14 if you keep letting him ignore you,' but, of course I said nothing and probably grinned inanely. It must have gone on for about 10 minutes. If ds had been upset I would have done something but he kept waving and saying, 'bye!' when he went past me but it seemed a bit sad - was also doing a funny run (love him so much!) and I felt I should have helped him.
Anyway, I sat down to feed ds2 and she didn't follow. Our 2 ds then came near me and hers pushed mine enough to make him stumble again and I thought he said, 'fuck off,'. I then clearly heard him say, 'piss off' and he pushed him again. I walked over to her and her ds then hit mine in the face. Again, not hard but obviously not a pleasant experience.
I said to her, 'I think ds is bored of running after yours now, can he have the ball back?' She said yes and went to get it, it didn't go well she had to chase him around and he was quite rude to her.
It all looks so trivial written down but it has played on my mind all day. Should I have intervened sooner and should I have told her about the aggression and swearing? She seemed a bit pathetic more than anything, desperate to talk and with no control over son. She wasn't intimidating yet I let her son run rings around mine