She took a pic within 30 seconds of the plane coming to a stop which appears to show the slats not deployed. Is it unusual for the slats to be retracted so quickly in a situation such as this?
Flaps retracted in after landing checks? If the slats were not deployed for landing this would be a non normal to say the least!
On the B737 have had at least one case where a cable to nose wheel steering failed which stopped us going anywhere - but we avoided the grass - just one possibility?
From Wiki:-
On 12 July 2012, Monarch announced that it was to wet-lease two B737-300s from Aurela and Small Planet Airlines as well as two B737-400s from Air Explore and Air Italy from the end of July to be able to offer additional flights during the peak leisure travel season in the UK.