Auctioneers in Ireland keep the deposit as a good will gesture just to show that you are interested in purchasing the property, however the vendor can and will screw you down the line for more money as the scenario is there is another buyer that is interested in the property and you will have to increase the purchase price to be able to buy, I should say you will probably get your deposit back from the auctioneers after he/she has drawn out the process as long as possible.
You have no guarantee that the sale will go though and the only time you can feel secure is when contacts have been exchanged with respect solicitors. Lovely process buying in Ireland!