I'm sorry for taking so long to respond (I don't have a Chromebook handy so I had to ask the product team). Here are the instructions I received:
To see the saved images of gallery:
1. Open ES File Explorer on Chromebook.
2. Navigate to “Home” folder and then to “Images” (or “Pictures”).
3. There will be an “Adobe Photoshop Sketch” folder; the image will be in that.
This was on an Asus Chromebook, but the instructions should work for you. If they don't, please let me know which Chromebook you're using.
I hope that helps.
Thanks so much! Made me realise what is going on here.
Of course, because Sketch is working as an Android app on a Chromebook, it is not visible in the normal Chrome file system but only within the Android part that is created when you enable Android apps. (That's also why the only "share" option was through Skype, as this is the only other Android app that I have installed.)
Solution - install an Android file explorer and use that to find the Pictures folder within the Android system. (Android on ChromeOS does not have its own explorer.) There is the exported drawing. Done!
A couple of additional comments. - I wouldn't recommend ES File Explorer now - it was in my mind great but is now full of bloatware. As I didn't need any extra functionality I installed the tiny and open-source OI File Explorer - available at https://play.google.com/store/apps/details?id=org.openintents.filemanager and that did the job fine.
Last thing - as we are needing to access the ChromeOS file system to see the Adobe folder (or any other folder within the Android setup), the other way to do this without installing an Android file explorer is to enable Developer mode and enable debugging options. Bit of a sledgehammer option but worth knowing perhaps.
I"m glad you have access to your saved files now.
I'm sorry I'm a bit ill-equipped to have a more two-sided conversation with you about Chromebooks... I have actually, on Android, also had to enable Developer mode to access some features so I completely understand your point about it being a "sledgehammer."
I'll share all your comments with the product team.