Search does not return all files

That's correct, there can be a delay on search results for recent changes due to indexing lag. 

Depending on your use case though, some other endpoints may be more useful to you.

For instance, since you mentioned you're uploading via the API, note that the /2/files/upload endpoint returns the metadata for uploaded file directly in the response for the upload call, so you can use that immediately upon finishing the upload.

Or, if you know the exact file path or ID and need to retrieve the metadata again later, /2/files/get_metadata would be the best way to get it.

Or, if you know what folder(s) you need to list specifically, you can use /2/files/list_folder[/continue] instead.

None of the above are subject to the same delay that the search endpoint is.