An unlock failed. Was I charged for it?

No. Your credit balance is only debited once a character's full art and story have actually been produced and are ready to show you — never before, and never for an attempt that didn't finish.

If your connection drops partway through an unlock and you're not sure whether it went through, just try again from the character's screen. Multiverse Explorer recognizes a retried request as a continuation of the same attempt rather than a brand-new one, so you'll never be charged twice for the same unlock.

If a character still looks locked after a failure

Check your credit balance in Settings first — if it's unchanged, nothing was taken, and it's safe to try unlocking again.