A simple argument that hydrino, i.e. "small hydrogen" may exist This paper discusses a possible existence of subquantum levels and hydrino, i.e. "small hydrogen", which may have been created during the Big Bang before formation of normal hydrogen.
Author of the study J.Va’vra from Standford university argues, that spontaneous transition from normal level to small level is unlikely because of a large electron energy difference in both states (254.16 or 510.17 keV). But the small hydrogen may be formed differently; for example, using a relativistic electron with a correct wavelength latching on a proton. Such condition may have occurred during the Big Bang, or during other very energetic and luminous events in the Universe.
One could try to use a high intensity electron beam of precisely tuned energy, and look for a sign of e-p bonded state formation. If the small hydrogen is formed, it would appear as a neutral object from some distance. Such object might be able to enter the boron nucleus in boron-based detectors, destabilize the nucleus, which may produce alpha particle, which then would be detected. However, this process might turn out to be very unlikely because the small hydrogen does have a fairly large size compared to nucleus size, and it has an electric dipole moment, which may prevent entry into the nucleus.