Photoshop :: CC - Ones Saved As JPEG / Appeared Tiny Instead Of Full Screen?

Just come back from a lengthy trip with about 900 photos from 3 different cameras. Did most of the jpeg's in LR 5, but waited with the Canon raw files for PS CC. All appeared to go well, with first adjusting them in PS CC camera raw, then opening some on PS CC. Saved most in PSD format. However, some of the less important ones, such as information photos, were saved as jpegs, from within PS CC.
 
This is where the trouble started. Once finished, I went through them all in Bridge, using full screen preview. The ones saved as jpeg, appeared tiny, instead of full screen. Trying to open them, resulted in an error message, with something about a marker not being there. Before panicking, changed the extension from jpeg to psd - and the filed opened in PS CC without any problems. Saved the files as jpeg, using a different name and this time they were all ok.
 
So it would appear that there is a problem saving a file with layers as a jpeg, without first saving it as psd