I've been traumatized

As some of you may know Andy and I have been going through the process of becoming foster parents. There are times, thankfully they are few and far between, (the last for Emily was when she was 15 months old and got into a nest of fire ants) when I feel like foster care shouldn't let me keep my kids much less be giving me theirs. Today was one of those days. I kept my nieces and nephews this morning for several hours. They are taking swim lessons at Richardson's Lake and of course got Emily and Jacob excited about going with them this evening and swimming after their class. So at 3:00 PM we loaded into the truck and headed off to meet them there. On the way there I realized I had grabbed the swim bag but not my purse. We didn't have enough money to get in. When we got there I explained to the cashier that I needed to go in to borrow a dollar from my sister. We walked in and Emily wanted to go over to the water slide to swim. I explained we were going to wait until their swim lessons were over then we would come and swim at the slide area. So we all walked down to where the swim lessons are and I borrowed the dollar from Tonya. Jacob stayed with her while Emily and I walked back up to the cashier, Emily had to potty and the bathroom is in there also. On the way out of the club house she wanted to go over to the water slide again. I again explained no we are going to go over to where the swim lessons are and wait on her cousins. At this point there was only 15 minutes left in the class and the kids (Sam, Edie, Emily, and Jacob) could play in the water over there. As we walked up to the area where the class is Emily asked if she could get a treat from the bucket and I said yes (Ms. Felicia has treat buckets set out for the kids). Jacob started crying, he fell under the water and Tonya was picking him up, so I hurried over to get him. A little while latter, probably 5 minutes I realized Emily wasn't anywhere around. OH MY GOSH!! My heart dropped. Tonya and I started looking and screaming for her and I ran up to the club house to get help while Tonya sent Sam and Edie to look around the lake for her. As soon as they had paged her I turned around and saw her on the platform for the high dive coming back toward the swim lesson area. My 4 year old had walked half-way around the lake to the slides without anyone and I hadn't even noticed she was gone.