The common cold is not a single virus but many many many different strands which are continually mutating. Ever gotten the flu after the vaccine? That's because the vaccine doesn't target all flu strands, merely what the developers identify to be the main strands of the flu virus for that season.

These particles are very difficult to find, extraordinary amounts of electricity are required to create them for the brief period of time they exist independently. Incredibly sophisticated equipment is used to detect the signs that such particles emit, and mind boggling computational power is used to sort through the petabytes of data gathered through thousands of collisions to be able to identify a particle with sufficient confidence.

Due to the unchanging nature of particles and their components, and the robustness of experiment methodology, and theoretical models to assist what one may look at, finding a particle becomes practicable.