Two Failed Sentinel Lymph Node Tests

I was recently diagnosed with a thick melanoma tumor, and I just had my local wide excision.  They attempted for a second time to try to find my sentinel lymph node using the injected radioisotope solution.  The surgeon used a gamma probe this time, because they thought they had located something, but it just turned out to be what the surgeon thought was probably a lymphatic vessel and not a node.  For some reason the solution just won't stay in my nodes and just washes through.

 I have my appointment with my oncologist in three weeks.  This is a real setback in determining a therapeutic course for me, I assume.  I wonder if I can get into any clinical trials now.  Has anyone else out there heard of this situation, and would you have any recommendations?  Now I will be unable to remove a lymph node if I do have microscopic deposits in any of my nodes.  I don't have any palpable nodes at this time, and PET and CT scans came back clear.  My surgeoon says that an elective lymph node dissection is not recommended.  This is so disheartening.  I was afraid of the results, but now the inability to know is almost as bad.

Just for helpful clarification for any other people reading the messages, they did do the two lymphoscintigraphy attempts before my WLE.  Apparently the biopsy was too severe an incision and disrupted the lymphatic flow. 

My appointment with my oncologist will determine what systemic treatment I get, but I'm leaning against interferon because I am afraid of the depression side effects, and I have severe reactions to anti-depressants.