How did you create your bootable flash drive? Did you use unetbootin, pendrivelinux or some other software?
The .iso version of Ubuntu suggested 2 partitions, 1 for Ubuntu plus 1 of 1 Gb for future changes. And I think I left one for the old files & Debian.
The above would be for creating the bootable flash drive persistence becasue 1GB is not much for future changes on a hard drive. From the information you posted, it is not clear that you actually installed Ubuntu to anything other than the flash drive. Did you boot the computer from the flash and go through the entire installation process for Ubuntu 12.04 which, when completed gave you a message indicating so and advising you to reboot?? Did you select the default option for the bootloader install?
If you have booted the flash drive and downloaded the bootinfoscript, you need to run it per the instructions on the site BEFORE you reboot. You are using a Live CD on a flash drive which is read only. When you reboot, anything you downloaded is gone.
Answers to the above questions should help to get someone to help you. If you can't answer them and you have no data on the Acer, try to reinstall.