  A universal dimer is subject to secondary collisions with atoms when formed
in a cloud of ultracold atoms via three-body recombination. We show that in a
collisionally opaque medium, the value of the scattering length that results in
the maximum number of secondary collisions may not correspond to the Efimov
resonance at the atom-dimer threshold and thus can not be automatically
associated with it. This result explains a number of controversies in recent
experimental results on universal three-body states and supports the emerging
evidence for the significant finite range corrections to the first excited
Efimov energy level.
