Is it hard to fight a theft charge?

While at a store today doing some shopping there was a book my boyfriend was interested in. So without him knowing I hid the book so he wouldn't see it to surprise him with it when we get home and continued to shop. We finally finish shopping and get in line by this time I had forgot about the book in my cart. Due to just having surgery the day before and by that time was in a lot of pain and just wanted to get home, now we are both facing theft charges for something I intended on buying but forgot about it. But the store wouldn't listen to me and is charging us anyways. They said since I hit the book that is intent to steal. When asked them to prove this was my intent with surveillance they wouldn't and refused to talk further and called the cops. This is my first offense but my boyfriend has a theft charge pending to be expunged. The store also barred us for life.