Why is filetype not set after :find from autocmd?

Question

Objective

I want vi file to act like :find file if file doesn't exist.

That is, I want to be able to edit a file by name, without giving a path to the file, from the command line:

mkdir -p a/b/c
touch a/b/c/foo.py

vi foo.py

When there is no file at all, I don't expect this to work. But when a file does exist, I'd like to be able to get there, just as I could with :find foo.py.

Implementation

I have set up my path in a local vimrc file:

let proj_dir = expand('<sfile>:p:h')
setlocal path=.
let &path .= ','.proj_dir.'/**'

Then I added a function in $MYVIMRC:

function! Find_if_not_exist(path)
    if ! filereadable(a:path)
        try
            execute ":find! ".a:path
        catch
        endtry
    endif
endfunction

And hooked that in with an autocmd in the same file:

autocmd VimEnter * call Find_if_not_exist(expand('<afile>'))

This almost works. The file gets loaded if it exists. But when Vim opens, the filetype is unset, there is no syntax hilighting, etc.

If I just type :e! again, the reload does get the correct filetype, syntax, etc.

If I type :find! file directly from my keyboard, it works.

So why does the :find! executed from inside my autocmd not get the correct behavior, and how can I fix it?

Edit:

As a temporary fix, I've added | do BufRead to the end of my function, which gets at least some of the problem resolved. But I'd still like to know what's going on, and if there's a smoother way to get the file loaded.