Is there some prior experience these coaches have had with you that may lead them to the conclusion that you are not a pitcher?
I support @Roger 's idea about requesting bullpen time from the coach. Before you do that, be sure that you have prepared yourself for the 'tryout'---which essentially it will be.
If you have not been throwing on your own for some time now, then you may want to hold off on your request until such a time when you will be at your best. Only you know what you have been doing on the side to prepare for your opportunity.
Make the most of it by preparing yourself for it.