Stable natural helium hydride?
As explained in Emission Spectra of Bound Helium Hydride Physical Review Letters vol. 77 pages 2941-2944:


  The ground state [of neutral HeH] is repulsive, as shown by
  numerous experiments and calculations.


but excited states of HeH that are bound exist (as first experimentally observed by this paper, but previously calculated).

Given that only excited states are bound, it don't think it proper to say HeH stably exists under any conditions natural or otherwise.  

The paper does state:


  Because of the abundance of He and $\ce{H_2}$ in stellar atmospheres
  and interstellar space, HeH is expected to
  be formed there. Therefore our data may be useful to
  find the HeH lines there.


However, that it exists does not mean it stably exists.