Whose Poop is This

I have just had my biggest parenting failure thus far.  I am going to potty train Mary Scott in a couple of weeks once school is out, but we have been talking about the potty with her for a while.  We have a potty seat and we talk about how you get candy when you potty and I let her sit on the potty if she initiates it.  Well, she has started to tell me when she has a poop and will say "ucky diaper" and wants me to change her, which is a great sign that she is ready.  
Well...... this morning she told me "stinky" before I was about to leave for work but when I checked her she hadn't gone so I let her sit on the potty.  I thought she was straining, but she didn't say or do anything so I let her sit for a minute and then got her up and didn't think much about it.   When Kevin got home this evening, he went into the bathroom and asked Whose poop is this?  Her chair was still on the potty where I had left it,  so come to find out she had gone some this morning and I had missed it!!   I felt like a huge failure!  I just never expected her first success to be a poop and so I didn't really look into the toilet.  Needless to say, we just got her up out of the bed to celebrate and show her where she had pooped and gave her some candy.  She was very pleased, but I still can't believe I missed it!!  Lesson- Make sure you look ALL THE WAY into the potty!!