Being offered the property you want and lost to a higher bidder is a good sign. You've been invited back to the table. Since your concern is with the listing agent and (thankfully) not your own, express your concerns to him or her and ask how they can ensure your offer is (actually) presented. The issue and responsibility of presentation belongs to your agent - not you as the Buyer. And your agent "should" be able to present your offer directly to the Seller unless the Seller objects to such an arrangement. Additionally, if your agent suspects something is going array, they can enlist the assistance of their Broker who can contact the listing agent's Broker.
Again, being invited back to the table is a good thing! Best of luck to you, and let us know how it goes.