Was this on e-bay? Is it an UK based company?
serious companies all have automated reply and ordering system, so not to hear at all from them makes it a bit dubious.
they have your bank details now anyways, so if they are to commit any fraud, they already have what they need.
even if they do not have any criminal intentions it is not really clever to replace an order with them. who is so disorganised to lose an order in the first place, will cause problems with shipping, refund and service in the second place as well.
long story short: don't!
cheers
carsten