Firmware images are now included in the Flirc GUI app starting with version 1.0.5. You can use this new feature to update your device to the latest release, or upload an image should the device be 'stuck in bootloader'.
Follow these simple instructions.
Open up the GUI and head over to the advanced menu.
A window should pop-up, which looks like below. Click on the button that says: "Force FW Update"
You will be prompted with a message to confirm. This window will tell you your current firmware version, and the one which is currently available. Because the firmware images change timings, there is a possibility you will have to re-learn keys. There is unfortunately no way to migrate these changes.
If you are using Windows, and if for any reason this fails or there appears to be no device in the GUI but "flirc" or "bootloader" is present in the device manager, it may be possible to fix this by re-installing the GUI which will also install the driver again. If that does not fix the 'device disconnected' message, then try the driver trouble shooting section of this website.