Keep the cheque, you can represent it upto THREE times.
Phone the customer, explain what's happened; it's probably just an oversight on their part and ask them when it would be a good time to represent the cheque.
Or you could just wait till the end of the month, and represent it then; hopefully by then there will be funds in their account to cover it. I once did this with a £50 cheque for someone who lived in a lovely converted school house. Guess what, it bounced again. He would've been charged £35 x 2 for the bounced cheques = £70 plus he paid me in cash £50 for the job I'd done. Total cost = £120 for a £50 job.

I think I cleaned his house once more after that and he sacked us!
