I’m not entirely certain what exactly you want to achieve. Do you want to refer back to a footnote that is defined elsewhere (doesn’t matter if it’s earlier in the text or later)? In that case you can use a \label and then use \ref to refer to:
This is some text.\footnote{\label{footlabel}%
This footnote contains some awesome proof.
}
As shown in footnote~\ref{footlabel}, this is true.
Note that you will have to compile the document twice.
If what you want to do is create the footnote – i.e. have no conventional footnote at all but have Ref. 4 as the only reference to the footnote (which in this scheme is really an endnote), you can do the following:
\def\endnotemark{\stepcounter{endnote}\theendnote}
Ref.~\endnotemark\ shows that this is true.
\endnotetext{Here is my awesome proof.}
The class you’re using links the footnote counter to that for endnotes, so there is no problem with the counters and you can still use \footnote and have it display the way you’re used to.
That said, I would still advise you don’t do this. It’s not how readers expect footnotes to work. What’s more, seeing as your journal puts out a style sheet, the editors might view that as a breach of that style. Either reference an existing footnote or, if that is not an option but the proof in question is still important enough to mention in the text, then why not put it in the main text to begin with.
MWEfrom\documentclassto\end{document}