money is never truly lost

In fact, money is printing every day more and more. So technically there is more of them every day. Which decrease their value and then we have inflation.

But, ideally, with each day, more useful products and services are being made and delivered. It'd be useful to have extra dollars around to account for more stuff being made and more things being done. Thus having more dollars in existence doesn't necessarily mean the value of a dollar is decreasing.

What does cause inflation, however, is when more dollars are printed versus things being made. You can't precisely measure the latter, so you have to make do with price indices and such. Which makes inflation hard to actually gauge, especially when everyone expects more and more to be produced every year (i.e. they expect their savings and investments to appreciate/gain interest) so you have to print more dollars to at least keep up the facade.