This appears to be in the Accounts Receivable module. Did you process the invoice with a payment? Try going to the related invoice and bring it up on screen. Is it pay later? or one of the other payment methods that would mark it paid immediately? Open this journal entry, is this the entry you are trying to look at?

I'm trying to open the journal entry and I get the error message.

This must be the Journal Entry you deleted. Carry on searching the Journal Entries and you should find one that is for the same dollar values only reversing the debits and credits. The message on this entry will tell you which entry it is reversing and what the new Journal number is currently. If there is only a reversing entry and no new entry (which is what I would expect as your deleted the original entry) then you must make a new entry not correct the one in error as it has already been deleted.

This must be the Journal Entry you deleted. Carry on searching the Journal Entries and you should find one that is for the same dollar values only reversing the debits and credits. The message on this entry will tell you which entry it is reversing and what the new Journal number is currently. If there is only a reversing entry and no new entry (which is what I would expect as your deleted the original entry) then you must make a new entry not correct the one in error as it has already been deleted.