will not start
 

last night my 2001 300 would not start it would only turnover, i had it towed to my mechanic he looked at it and found no spark, as he trouble shot this he noticed that my key the open door/lock button was missing,as we found it under the seat we put it back together and he left for the night... the next day he was trying to unlock the doors and as he did he noticed a red blinking light security light on the dash so he tried and the car started.
do these cars have a security that will not let the car start and if so is there any issues i should be ware of.

The key fob needs to be near the ignition or the car will not start. Check your owner's manual.