Search by ID in the CP
If you analyze POST request you will see this:



To get items by id you need to create custom request and add criteria[id]=(int id here) e.x. use this

It is most likely related to the way how ElementCriteriaModel works (99% sure) :

craft.entries({
    id: 123, // search by ID*
    search: 'search query'
})


search by ID*

craft.entries returns ElementCriteriaModel - Source

You won't be able to use default CP search form to get entries by ID