Validity and Anaphora

The following argument appears valid:

Some deity is called 'Zeus.'
Zeus is wise.
Therefore, some deity called 'Zeus' is wise. (D. E. Buckner, Reference and Identity, 118)

Now if an argument is valid, it is valid in virtue of its logical form.  What is the logical form of the above argument? The following argument-form, Buckner correctly states, is invalid:

Ex Fx
Ga
Ex (Fx & Gx)

So if the form just depicted is the only available form of the original argument, then the validity of the argument cannot be simply a matter of logical form. And this is what Buckner concludes: "It is clearly the anaphoric connection between the premisses that makes the argument valid, but no such connection exists in the formalized version of the argument. "(119)

Buckner seems to be arguing as follows:

a) The original argument is valid. 

b) The only form it could possibly have is the one depicted above.

c) The argument-form depicted is plainly invalid.

Therefore

d) The validity of the original argument cannot be due to its logical form, but must be due to the anaphoric connection between its premises.

I do not find this argument rationally compelling. (b) is rejectable.  I suggest that the original argument is an enthymeme the logical form of which is the following:

1) For some x, x is called 'a.'
2) For any x, if x is called 'a,' then x =a.
3) a is G.
Therefore
4) For some x, (x is called 'a' and x is G).