What is the quickest way to defrost a vegetable curry without a microwave?
Extract it from the container (run the container under the hot tap to loosen up the edges if necessary) and put it in a saucepan. 

Add a little bit of liquid (water, juice from canned tomatoes, milk... whatever would go with the particular curry you have) just to cover the bottom of the saucepan so it isn't getting heated dry. 

Put it on the stove on a medium heat.

Use a sharp, serrated knife to saw the "frozen lump" into smaller bits, being careful if you have a non-stick saucepan not to scratch the pan surface (you can saw half way through and then prise the halves apart carefully instead of sawing right through the lump).

Keep stirring and turning the lumps over so all sides are getting heated. As the lumps start to loosen up, keep sawing them up into halves. 

Within 10-15 minutes all the lumps will be gone and you can make sure it's thoroughly heated through before serving.