Spin liquids are intriguing magnetic states of matter that are neither ordered (like ferromagnets or antiferromagnets) nor disordered (like paramagnets), and require new concepts such as fractionalised excitations and emergent gauge fields for their description. A complete understanding of such states is still lacking and many fundamental questions remain. Quenched disorder can nucleate defects with unusual properties and thus reveal the hidden collective excitations of such spin liquid states. In this talk, I will first give a brief introduction to spin liquids and then explain how disorder can act as a powerful probe for the diagnosis of certain types of spin liquids by (a) producing spin textures with fractionalised moments and (b) leading to a topological spin glass which shows signatures of both spin liquidity and glassiness.