It would be worth consulting with a personal injury attorney to evaluate the situation, but you may not have a claim.1) If the escalator was defectively designed or manufactured, you might have a product liability claim against the maker; or if defectively installed and maintained, against whatever company(ies) do the installation and maintenance. However, if the escalator was designed, manufactured, installed, and maintained properly, there would be no liability. The fact that there was no visible stop button near you does not by itself mean that there was a defect--it depends on what is considered proper for an escalator.2) The store would likely not be liable for the injury unless you can show that they were negligent, or unreasonably careless, in some way (such as by not having the escalator regularly maintained, if a lack of maintenance contributed to the injury); without fault, they are not  liable.3) The store is not under a legal obligation to call paramedics or 911--the law does not require people or businesses to assist others, as a general matter.Note every time a person is injured is there a legal claim: there must be fault, and there also must be violation of some duty or obligation.