I accidentally cancelled the wrong invoice! How do I "un cancel" an invoice?? HELP!!!

[Boho66]

I sent my customer an invoice. I didn't think it went through so I sent her another one several days later.  She paid the first one & I accientally cancelled the one that she paid!  She has given me proof that she paid it plus she is a good friend, no fraud or scam going on here.  The $ never reached my account.

How do I "un cancel" that invoice?? 

[kernowlass]

@Boho66

If it was cancelled then the funds should go back to your friend, when they do she can pay again.