So in other words, you cannot access your Google Voice number.
That should be solved simply this way:
Use a computer. (Not a library computer, this sort of operation is usually forbidden on one, since it involves installing a plug-in... but some librarys might permit it.)
Log in to a GMail account associated with that Google Voice number, on the computer.
(Install the Google Voice plugin if needed, or if not needed, just read the Google Voice voicemail that has the code for the 2-step verification.)
That should get you past the difficulty... but I suspect it may not be so simple... let me know if there is a snag or problem with this proposed recovery process.
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