[jdurg]

I always had the impression bicarbonate ion can only exist in aq solution. there is no such thing as NaHCO3 (s).

Have you ever wondered why there is baking soda and baking powder?  One of them is sodium carbonate and the other sodium bicarbonate.  (Though I can't remember which one is which).  

For the original question to this thread, the right answer all depends on how hot the bicarbonate is heated.  If you heat it to a high temperature of about 270 C the CO₂ is driven off and NaOH remains.  If the temperature is lower, then water is driven off as well.  The reason for this seemingly backwards reaction?  Beat's the tar out of me.  

[AWK]

Solution of NaHCO3 start to decompose at about 50 C, solid bicarbonate at about 100 C
according to reaction:
2NaHCO3 = Na2CO3 + H2.
Decomposition ends before 200 C. So heating NaHCO3 to 270 C without decomposition is eventually possible at CO2 atmosphere (I am not sure) but, for sure,  not in Bunsen burner.