We are aware of the inaccessible collapsed sidebar in Baldur's Gate: Enhanced Edition on iPhone. We are working hard on getting an official fix released for this issue, but in the meantime, you can restore the sidebars by activating the Zoom function on your iPhone:
Settings > General > Accessibility > Zoom
A three-finger tap will bring up the zoom window, and a three-finger drag will scroll it down to the bottom of the screen which will allow you to restore the sidebar.
This is far from an ideal solution, and we will get the official fix released as quickly as we can.
Thank you for your patience.