How to mend a broken coil in a DC motor?
If I understand you correctly, I think shorting the commutator plates for the dead pole to the adjacent working one (either side should work I guess) may actually be worth trying. 
With more than e.g. 3 poles it should be okay as you won't short across the input as the brushes touch both poles.
Since your motor appears to have a lot of poles it may still work okay if one pole has to cope with twice the angle. At least there will still be field as opposed to it dropping out completely.  

Take advice with caution (i.e whatever you try, make sure you do it as safely as possible) as it's hard to be sure of anything in situations like this when you have no datasheet available with relevant info like winding connections. 
Before you apply any power, turn through all poles and test to make sure there are no obvious shorts where there shouldn't be (e.g. across the power input) and resistance doesn't change much from the 50 ohms you measured across the working coils.  

Of course, the sensible option is just to buy a new one (for actual serviceable use) as Olin says, but even then I'd probably still hack this one just out of curiosity ;-)