Lost incoming emails during "upgrade" to MS Exchange 2010

Our email service was down last week for two days while Comcast upgraded our email Exchange to 2010.  We have never received the incoming emails that were being sent to our 10 email accounts during the outage.  None of the senders received an error or bounce back message during the outage either.  Where are those emails?  We need to know what people were sending to us !!!