Framed wrongly in a fraud case

Sir, I work in a very prestigious govt. company and was in purchase deptt. at the time of fraud. The vendor alongwith some of the office staff committed the offence by manipulating the data of purchase orders at the end of server.e.g. if an item was ordered at Rs.50 per unit, then it was changed to either Rs.150 or Rs.500 and then its printout was taken and forged signature done on it and used our seal. All the logs of this manipulation were then vanished from server. This way the vendor committed this crime. Since we used to place orders using the data available in server, the orders placed by us were on wrong rates (which we were not aware of while doing our job since there was no point of doubting on data available in server). This thing came out during investigation after 4 years. The IO investigated the case in a wrong direction and could not identify the root cause i.e. who did these manipulation at server end and thus made us accused by charging sections 120B, 420, 468, 471 of IPC and 13(1)(d) & 13(2). Kindly confirm how should we present our case in court or what could be the possible ways of coming out from this situation. Thanks in advance.