If I'm not incorrect the stock ECU in Syclones, Typhoons, and Sanoma GT's are all some form of ROM. Which is read only memory. I could be wrong, and its possible they are EPROM. Which is Erasable Programmable Read Only Memory. And for that matter they could also be Prom. Rambling here, but essentially the memory that the Turbotweak chip uses, I believe,
can be reset to default settings via disconnection of the negative battery. Which is often times why its best to save the tuned settings to a device or export. So you can either input the settings of your tune back to the chips after they have been re-set to their default settings. Or import them, if the chip offers that feature. The tune is sometimes (Or settings of the ECU) are lost due to the fact that ECU's at the time had, (hopefully this is the correct assumption) no default power to rely on. Without power, the read only memory would be lost after a period of time.
To add to this here as well, its a common misconception that all ROM is completely Non-volatile, that is not correct, and in this case comes down to what type of chips are being used on the Turbo tweak chip. Small portions of the ROM may be volatile, the larger part may not be and vice versa.
A good example is computer motherboards. Motherboards often use a CMOS battery to store the user settings of the computer BIOS and CMOS, much like a car, when that power source is removed (Power supply Unit, and CMOS battery), the settings revert to their default after a period of time.
I'm generalizing the topic but this article
here summarizes the concept of what happens very well.
It is also possible that somehow, the battery being disconnected and re-connected was causing an in-inadvertent electrical wipe. So when there is a surge of power back to the ECU, although the memory on the aftermarket chip may be stored in Non-volatile memory, (meaning its not supposed to be erased with the withdrawal of power) it can still be corrupted/deleted because of a surge of input power. It is common to see this also occur on computer Hard drives and SSD's as they utilize a similar chip based input. However, I believe that may not be the case in this specific situation. But as an example its very useful not to overlook the fact that its possible, its just not likely here.
I'm not able to defer what the whole situation is with the ECU, I'm making assumptions here on causes. It could be an innumerable amount of things but from the short description it seems like this information may be relevant to what occurred.
I apologize if there is any sort of mis-information here, please correct me, if you find anything incorrectly explained
.