Not a stupid question. Good to ask what you don't know.
Yes, we're talking about startups with their operating capital frozen and struggling.
Many of the commenters here appear to be confusing bank depositors with bank investors. If you started a startup, it's very likely that your funds would be frozen.
> And how can a bank 'loose' money from checking accounts
As usual, it's complicated. Banks have always used the money in checking accounts to make investments. All of the service fees are just a tiny fraction of how a bank makes money.
The real question is how - and to what degree - a bank should be able to invest that money without creating untenable risk. Essentially, they are allowed to loan a significant multiple of their actual cash holdings.
Let's say that they can loan $5 for every $1 in trust. This works great so long as they don't have 21% of their customers show up and demand their holdings at the same time... which is a drastically simplified version of what happened late last week.
Unfortunately, they don't teach this stuff in high school. They 100% should.