I agree you probably lost the heating element. They are not hard or expensive to replace. You will need to buy the replacement element by providing the model and serial number to your local appliance parts dealer. The part may come with instruction. Generally, unplug the unit and remove the cover inside the dryer on the back of the drum. That should expose the element and mounting screws. Make careful note of the wiring attachements and replace the element. If you run into problems call a serviceman. That should be the first step if you have any doubts.
Dan O may have some additional ideas on his web site to refer you to. He is our virtual appliance expert.