Full Idea
Identity statements are about objects. If we can say that 1 is identical (or not) to 0, then 1 must be an object.
Gist of Idea
Identities refer to objects, so numbers must be objects
Source
report of Gottlob Frege (Grundlagen der Arithmetik (Foundations) [1884]) by Joan Weiner - Frege Ch.4
Book Reference
Weiner,Joan: 'Frege' [OUP 1999], p.59
A Reaction
This seems to point to Platonism about numbers, but maybe we can accept it as being about physical objects. If numbers are essentially patterns, then identity is hypothetical one-to-one identity between sets of objects.