Another symptom of Phobos being so close to mars is that objects on its surface are not all in zero G. On average, object at the same altitude will weigh about 0.285 kg*mm/s less per kg on the day side than on the twilight one, with a gravity sometimes dipping under 2 mm/s^2, this could have noticeable effect on escape velocity.
Additionally, Phobos escape is not really necessary to escape Phobos, a jump above Stickney crater that would launch you all of 3 centimeters up on Earth would be enough to get to the Lagrange L1 point between Phobos and Mars. So you would than be in zero G, and never fall back down (staying in mars orbit) (although this jump would take around half an hour on the way up).
So, an astronaut trying to move around on said crater would be nightmarish without some sort of rocket pack, Let's say he bends over to pick up a rock, he gets back up over the course of 2 seconds, moving his center of mass 1 meter, he will now be moving a minimum of 1/2 meter/s away from Phobos, easily enough to reach L1 and go into a Mars orbit.
Let's say that (s)he tries to walk quickly, his/her center of mass moves at several tenths of a meter per second upward, in addition to his m/s forward, therefore, he moves upward and drifts again into Mars orbit.
Throw a 5 kg rock downward? go into orbit, throw it upward? still go into orbit, as does the rock, Here is the scary part, people on Phobos might lift not just that rock, but there lander if they try very hard at all.
Oh, and heaven help you if you thought firing a gun downward was a good idea! less than a half-second of assault-rifle rounds into the crater will send you to Mars orbit.
Or what if you puncture your suit? You might think you could just hurry up and be inside your pressurized spaceship within 2 minutes and you'd be fine, but nope, if it is facing upwards, air will rush out at 340 m/s, if it is escaping through a 1 cm^2 hole (widened by the pressure), you would lose 34 liters per second of air at 1/3rd sea-level pressure, even if your tank holds hundreds of times that, you still emit about 12 grams/s of air, accelerating you at 0.0408 m/s^2, enough to get to get to L1 with around 7 seconds of air released.
Oh, and don't even think about using golf to demo low gravity. 2 kg of metal flying back up at an appropriate speed could Easily send you into mars orbit.
As could a poorly balanced washing machine (send anything on top of it).
Diet Coke and Mentos rockets could reach escape velocity.
Forget diet coke and Mentos, Diet coke by itself might be able to Reach L1.
It would take only a few nukes to deorbit Phobos into mars, creating an explosion that obliterates whole martian regions.