Download of 15.10 fails to install

Had to use data plan on my phone because local net too slow and then WW (Ubuntu 15.10) failed to install or even save to the downloads folder of Firefox or my 14.10 downloads folder, twice.

Search doesn't reveal it ANYWHERE on my HDD and I am confused.

Connected to Ubuntu site, selected the new Ubuntu update (already have it on my desktop, but not on my HP laptop). It self-installed and should have on my laptop as well.

Bought the book - Ubuntu Unleashed with 14.10 disc available and that installed easily. I am just trying to update to the newest version instead of having to use the older one.

Is there a disc available for 15.10 now?

Net installations in rural area(s) seem to fail more often than not.

Suggestions or assistance would be welcome.