Can someone charge me for storage?

Long story short, I moved across the country approximately 4 months ago and before I left I was living with my parents. I left my 4-wheeler with them when I left and it wasnt a issue. Since then we have had a bit of a falling out (understatement of the century...I found out my mother stole from me to buy liquor) and now they are saying I can't have my bike back until I pay them storage fees for the time it has been there. I wouldnt think they could do anything because 1) there was no contract to pay storage, either verbal or written (2) wouldnt you have to give notice to someone that you're going to charge rent...they are trying to keep me from getting it back. Any advice would GREATLY help!!