There is a hidden recovery partition in satellites for recovery purposes. unless you reformatted before including this partition you could try holding the number 0 key whilst booting up.
If you have everything on the usb try pressing f10 or f12 whilst booting , go to the bios find an option called 'boot options' and switch the boot options to boot from usb drives.
From MY satellite, (L510) in the user guide they mentioned of holding the F8 key whilst booting to access extra boot options. Not sure if it would help, Im copy pasting it here. ^_^
About 1.5 GB hidden partition is allocated on the hard disk drive for the
system recovery options. This partition stores files which can be used to
repair the system in the event of a problem.
System recovery options
The system recovery options feature is installed on the hard disk when
shipped from the factory. The system recovery options menu includes
some tools to repair startup problems, run diagnostics or restore the
system.
You can see the more information about Startup Repair in Windows Help
and Support content.
The System Recovery Options can also be run manually to repair
problems.
1. Turn off the computer.
2. While holding the F8 key, turn the computer on again.
3. The Advanced Boot Options menu will be displayed. Use the arrow
keys to select Repair Your Computer and press ENTER.
4. Follow the on-screen instructions from this point onward.
Hope it helps! :D