Immobilizer light flashing while driving.

Hi guys i'm new here. Let me start by saying i'm looking at buying a car tomorrow but have some questions.
Today I test drove the car and was told that the key fob was lost and a replacement was programmed for the car to start...but not locks. But while driving it I noted that the Immobilizer / Theft deterrent light was flashing. Is this normal because everything i'm reading says that the car shouldn't even start. I know that the car isn't stolen because we are planning to take over the loan in the morning for the car at the bank. Can someone please tell me what I should do. If this is because the key was only programmed without the original then can I simply use this one until I can have Toyota make me a new key for around 350-400 based on what i'm seeing online. Any advice would be very helpful. Thank you.


Below is the light that i'm referring to (car with key in it).

 

Thanks for the info guys, I really like this car but don't want to jump into a bad mess. I'm not worried if I need to buy a key but just don't want a bigger issue. As for touching the start button. I didn't try this so I might see about that today. I had the key fob in the start slot while driving if that helps.I have come up with a simple plan to make sure nothing has been tampered with. I'll simply attempt to start the car without the fob present (15 feet away). If the car starts I'm out, if it doesn't then it's a Toyota new key and programming. What do you guys think.

 

Alright well it's now daytime here and i've been buzzing on the phones with every Toyota dealer around and afar for pointers. Turns out that this can in fact happen if the key wasn't setup properly and the funniest part is 3 dealers in the town next to me referred me to a Locksmith that does their cars for them.. I gave him a call and he said he would like to check it out but is positive it's just in need of a new key (possible ebay key currently being used). He will meet me at the sellers and will program on the spot for a total of $315.00 that is new key and programmed for all features to work and the light will go off he assures me. So before the sale takes place i'm going to gamble with the key cost and see if it in fact does resolve the issue. I look at it this way, in the end i'd be buying a new key anyways so might as well do it on the spot.

 

Well guys i'm proud to say that i'm a new Prius owner!. Key cost $340 total and light is off. I drove the care home and all is well. I do have a few questions because this is my first prius... Does the battery meter go up/down often.. I was in a drive through with the lights on and it dropped a few bars after about 10 or so minutes but charged right back up after a small drive..is this normal? Also my friend said that the shifter is odd.. When I put it in drive it clicks on the shifter (almost like plastic on plastic click) but only in drive. Thanks if you guys choose to help me with these questions.

 

Yeah I've been researching this issue, seems to be a warped plastic piece.... I wonder if I should have one cnc'd from light aluminum. Thoughts?

Ok as long as the battery dropping and charging as fast as it does is OK then I feel better... This car is a big switch from my 944 Porsche lol.

 

Babies, have to grow up fast and move past the speed days. But this car is entertaining me with tech so I'm happy.