I don’t know – you should make a copy of the .DATA folder before trying to open anything.
What date does the .DATA folder and contents show, at it may have already been overwritten? Copy the existing .enl file somewhere else, but it is only a pointer. A completely empty no contents, textfile with the libaryname.enl is really a pointer and doesn’t have to have anything in it to point to the right place in the existing .DATA file. – It may already be too late, if you openned it and closed it once? – I guess you haven’t backed it up?
Did you try “recover library” from the endnote tools menu?