If you have an emergency and live out of town, the box office will work with you.
If I were ticket window and you offered me your tickets back even though we have a no exchange policy I would buy them out of my own pocket money so fast you would be surprised. Those tickets are easily worth 5 * their face value. Sell them online or try and exchange them with somebody who has tickets for a date they can't use.
Just sell them
With a hot show like Dear Evan Hansen it might be harder to get a post date tickets if you miss your show. Ticketmaster does not offer refunds or exchanges. You should either sell or try to risk and ask Ticketmaster for post date tickets. Call them and ask about the procedures for this particular show.
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