The bank is only open from 9 a.m. to 12 p.m. on Saturdays.
After she walked around the bank and called out to employees, she discovered no one was there.
Police later showed up to see if there was foul play, but did not notice any signs.
It appears to be case of forgetting to lock the bank.
Check out the Lyanne's video above chronicling the experience at the San Francisco bank.