My upper radiator hose sprung a leak?

I know radiator hoses can go bad over time, but I had just checked them and there were no soft spots and seemed in good shape. Then I took it in to get the thermostat replaced and they told me I should change my hoses too because they were soft. I told them no. The today my upper radiator hose sprung a leak and when I looked under to the hood to figure out where the leak was coming from I spotted a piece of sandpaper stuck between my battery plate and lower part of my upper radiator hose. I thought that was odd. Not sure how the sandpaper got there. I don't want to assume anything, but could sanding the hose cause it to weaken and break? Just seems odd that three days after they recommended changing hoses it springs a leak. AND there is a mysterious piece of sandpaper in there.