There are two draft mail boxes on the iphone MAIL app.
One is drafts (immediately under the inbox folder) and the other is Google mail drafts. I am unable to edit emails saved under the Google mail Drafts folder even though it downloads all the draft emails that I can edit in Gmail (on the web via desktop computer).
New emails that I compose and save as a draft are saved in the first DRAFT box rather than the gmail draft box. I am not then able to access that draft mail in GMAIL via my desktop computer.