Michaela,
Do not beat yourself up over this!!! You did remarkably well. Your first attack was the fear of the storm, but you had your sister in law with you, also it happened at Wal-Mart. So when you went back, subconsciencely or maybe not, your thoughts drifted back to the attack at Wal-Mart, where you found yourself again. But no storm, no sister in law, but it was the place where it happened, so we associate the "place" with the attack. This is the beginning stages of agoraphobia, ONLY if you let it. Associating and avoiding places or doing these while having a previous attack. If your truly frightened about returning to Wal-Mart on your own, keep going, take someone with you, but let them stay in the car, but keep at it, to where you no longer fear the place and associate it with attacks. I found out the hard way one avoidance will lead to another, and my safe zone got smaller and smaller. I also learned, being my worst critic is the most damaging, if I proceed to make only 5 baby steps, good for me, Im not going to bring myself down over not having accomplished the world in a day.
Happy Easter,
Trish