Does air traffic control identify a distress situation when an aircraft flies triangles in the sky?
To my surprise, this does exist, at least in the UK. According to the Manual of Air Traffic Services:


  7 Emergency Triangle Procedure
  
  7.1 Pilots lost or uncertain of position and experiencing either transmitter or complete radio failure are advised, as a last resort, to carry out special procedures to indicate to controllers that they
  require assistance.  
  
  7.2 The aircraft fly at least two triangular patterns, before resuming course, as follows: 
  
  Table 1:
  
  
  7.3 If a triangular pattern is observed, controllers shall advise the D&amp;D cell of the position and track and continue to plot the aircraft
  whilst it is within ATS surveillance system cover. Controllers should
  also be aware of the effect wind may have on the pilot’s ability to
  fly an accurate triangle.


I say "to my surprise" because there are well-established procedures for comms failure under IFR and under VFR. But having said that, it's possible that the triangle procedure is more useful in the UK (for example) than the US, where there are usually plenty of uncontrolled airports around and many pilots have no need to talk to ATC anyway. In the UK, with a much smaller airspace, fewer airports and more ATC control (at least, that's my understanding), it may be more critical to give even VFR aircraft a "last resort" to contact ATC.