Please NOTE! FiatECUScan /
MultiECUScan can ONLY code new remote key fobs. It CAN NOT code new smart key chips into the system. Also this function is only supported on certain models and as far as I can see it is not supported on the Idea
This means that regarding your stolen key then the Remote Unlock will not work but the physical metal key will unlock the car and the smart chip will allow the car to be started.
You have some options:
1) Go to a Fiat dealer and ask them to delete / reintroduce any keys you still have. This will stop the stolen car from being able to start the car although physical access via the metal key will still be possible.
2) Having had 1) done then get a clone of the remaining key made. If you lose / get another key stolen then it is definitely new key from Fiat time
3) Doing 1) incur charges. A charge for the keycode card / NVSR code request process (unless you have a very nice and friendly dealer who want's to maintain your custom)
4) Skip 1) do 2) and have an *additional* immobiliser fitted to the car. Physical access will still be available to the lost key but they won't be able to start.
5) Find an Idea/similar car in a scrap yard where they have at least one key and then fit these locks and then do 1) and 2)
6) Find a fellow Idea driver with same problem and do lockset change and exchange the metal key blades but keep existing fob/chip hardware. Now do 1) and 2)
A minor complication with a DIY lockset change is that you have to remember not only are the door locks involved but also the ignition key lock barrel as well. I don't have an ignition key barrel on my Croma. Don't know about the Idea.
LASTLY be very aware of any insurance implications of NOT have a complete lockset change done. If you car is stolen or removed, even if this is done by a drive by pick-up and run merchant who never had access to the stolen key then you may find you insurance company won't pay up.
Modern car security has certainly reduced casual theft, increased theft by force for those expensive in demand luxury models, and bloody well increased the cost recovering from a lost/stolen key.
I have key cover on my car insurance and also on my Sentinel Gold card/key policy. Not sure if my car keys are covered on my house insurance policy under "all risks" or "stolen from home" sections.
Check every insurance policy you have for cover and claim on the policy (if any) that does the least damage to your insurance costs.
Best of luck.