Back to the original question. Yes, batteries can lose charge after prolonged periods of non-use. If it's plug in-able (is that a word?) plug it in and see if it charges up. If not, replacement batteries are easy to find.

I have an older Rascal that I 'inherited' from my mother after she developed Alzheimer's and could no longer use it safely.

I have found batteries at a local tire/auto parts shop for a lot cheaper than from the manufacturer or an online vendor. I don't think it really matters what name is on it. They're all manufactured in China, anymore so who cares?

And Frank's comment about cement floors is true. Never store an automotive battery on a cement floor. For some reason it saps the voltage right out of them. Not sure exactly why. Maybe the combination of residual moisture and "grounding". I just remember being told by shop teachers and shade tree mechanics to always place a battery on a piece of wood.