Chrysler Repair: Power assist on brakes, radiator cap, vacuum hose

Question
My 06’ PT Cruiser 2.4 custom, was running 100% when I took it in for the schedule maintenance tune up. When I received the car back they (the mechanic) had failed to properly replace the radiator cap, causing over heating at the same time, it appears during the service, they also broke the clips to the cover over the throttle arm. While I was driving the cover came off and wedged itself under the idler forcing it into full throttle, creating a runaway car, and making braking very difficult. Since this life threatening scary situation, a leak has occurred in my air conditioning, which again caused the car to over heat while spraying Freon  all over the engine. Now my air conditioning useless. About 2 weeks later the plug for the air intake, that supports the power assist on the brake, or as they referred to it, the “Grommet”., just fell out?? rendering the vehicle useless (due to it not having reliable brakes). “Just fell out”, This is what the mechanic told me, it is a Chrysler defect and I should take it up with them. This does not make any sense to me because for one it is a vacuum and for two, this potentially life threatening defect would have caught the attention of the manufacturer.
My Question is, is this an area “the grommet plug” which a mechanic would run checks on, while tuning up a car? Could the 2 previous overheating (not prolonged, occurring 4 and 8 weeks earlier) have caused this grommet to pop out? It happened while parked. Is this garage lying to me or just incompetent? How could this have happened? Your advice is very much appreciated.
Thank You

Answer
Hi Jennifer,
If the grommet is at the end of the vacuum hose where it joins the engine intake manifold where the vacuum in 'created', then about the only reasons for that to fall out would be it was removed in order to service a nearby part on the engine during the service work, or it may be that the grommet had been overheated by the prior overheating events such as to become brittle and easily dislodged. If the grommet wasn't changed you could take a look at it, try and pull it out of its socket to see how easily it 'falls out' and that would give you an idea as to how likely this was to be 'spontaneous'. The series of failures following the service would make me suspect this was also a human-induced event.
Roland