last month i got stuk in a mud pit , mud everywhere

and after a coupple of days may starting motor stopped working , the dealer said that there was mud in it and it couldnt work properly , so i had to change it . yesterday i was traveling on the highway ( and here are pretty fast

) and when i stopped at the gas station , the car wouldnt start again ....... i mean the starting motor was spinning but it wouldn engage the flywheel . I called the dealer and i told me i had mud in it again , but i didnt go offroading since the last time i had a dive in the mud , so the dealer told me that the speed can send some old mud stuck inside the engine on the starting motor
anyone had the same problem ? can you help me ?