Slipped in supermarket and dislocated shoulder

I slipped over on a patch of water in a supermarket around 4 weeks ago and badly dislocated my right shoulder. My partner made a complaint to the store manager at the time before taking me to hospital. The manager apologised but said a customer must have spilt the water as it wasn't near to any fridges or freezers that could have leaked. If this is correct and a customer had spilt the water, does it mean that the supermarket are not to blame for me slipping over and I would not be able to make a claim against them?

I haven't been able to work since it happened as I work in a factory and my job involves a lot of lifting. I only get basic sick pay so am losing money each week I can't work.