First there may be a reset button. This returns it to factory setting including the default password.
Second. if you did NOT use the same SSID your laptop may recall the PW and know how to connect to it (IF you did, well sorry)
I am on the chromebook just now so can't research how to "Discover" the PSK (Password) for the current connection but I know it can be done.
OH, one other way
IF you know the password to access the router's set up pages (Again often the default) Hard wire to it using Cat5 Log in and look up what you need. It is on the set up pages after all often under "Security".