Toni.... maybe your Mum can leave a blankie and a bowl of dry food (fishy flavour) in a dark box.... the kitten may smell the food and snuggle in the box because it is a food source. The kitten could have run under the house... or even under the car near the wheel shaft or engine.... that is where the kittens i have now used to hide.
Otherwise if you phone SPCA they can leave a trap to catch it .... the traps are gentle ... i have four kittens that i caught with a trap that SPCA loaned me. Hope she hears and finds it tonight. 
Edited by Shezzey