We have all been there, panicking about every phone call and letter while waiting for creditors meeting. Was probably posting hourly at this stage!! I know what it is like having so much riding on the decision. Just think there is nothing you can do now until meeting, don't make any payments (put money aside) and if get bombarded with phone calls tell them you are entering in to iva and try to stay positive. You will be fine !
It could be classed as a potential preference if they take the funds when they know you are insolvent and clawed back by any Trustee in Bankruptcy IF your IVA does not go ahead and you were bankrupted..
It's rare for the creditor to cancel the payment rather than you but clearly they have taken action having received notice of the IVA meeting.