WisG

Good evening all, I am completely new to this site and hope I'm putting this post in the correct place. Long story short-ISH.. I purchased a 63 plate Audi A6 Avant 3.0 Bi-TDI Black Edition (313) with 63,000 miles on the clock from an Audi dealer up country only 3 weeks ago. A few days ago whilst driving around in Plymouth (my home town) the car spun out of control on a slow-ish corner.. luckily we didn't hit anything! When we all got out of the car we realised what had happened.. There was a huge trail of diesel behind the car and the fuel tank was empty. The AA came to recover us and discovered that a low pressure leak-off valve pipe on top of the engine had popped off and in turn squirted all the fuel out everywhere. The AA popped the pipe back on, put a bit of fuel in and drove very cauciously to my local Audi dealer for investigation. (The car drove perfectly - no issues) 4 days later they finally told me what they had found.. They said they had to order in a 'special tool' to do some testing. They also said that injector 4 was faulty, causing cylinder 4 to miss-fire, causing the injector rail to be bent. They have not mentioned the pipe coming loose at all. They said I'd need a new injector and a new rail. After I heard this information from my local dealer, I emailed the dealer that I purchased the car from and asked if they found and problems during the 145 point 'Approved used car checks'. They came back to me quite shocked at what had happened and said the following: "During the 145 point checks, It was discovered that a low pressure leak off pipe had become loose and was then re-attached". So here is where I'd like an opinion from of you guys.. When the AA guy discovered the pipe had come off during recovery, I noticed that there was a small red dot on the hose ear clamp. I know these clips are a 'one-time' use style of clip because I use them in my job quite often.. Does the red dot mean that it's an original factory fitted part and that this wasn't replaced after it was found to be loose.. in-turn maybe causing the hose to pop off again? OR Is the reason the hose keeps coming loose something to do with the faulty injector causing a back pressure? I'm trying to figure out if this should have been picked up during the 145 checks when at the dealers that sold the car to me. I'm glad I was only doing 30-40mph instead of on the motorway when all the fuel dumped out! Any opinions would be much appriciated - Cheers