Good for you, milliec, for taking the time and effort to discipline your child, and to think carefully about other opinions ad options too. I agree with you, fwiw - I think it's a very unhelpful thing to do to pay for the toy. Pesha, I see what you mean about small children learning by rote and experience - they don't just wake up one day with the ability to understand a certain concept, they need to experience it many time. MillieC, I think you gave your DD an experience which will help her, in the fullness of time, to gain and understanding of who owns what, and what she can take and not take.
To be honest, I think the main issue is that she disobeyed you, and the 'stealing' (although I wouldn't call it that) issue is a side issue.
To those who say they'd buy it - what would you do if your 2 year old asked for a sweet, you said, 'no, not now', and then you found them 2 minutes later standing on a chair with their hand in the sweetie tin? Would you say "They can learn that lesson later!" and let them have the sweets, just to make them happy? Personally, I'd take the sweetie tin away.