from article:

Only particles of about 10cm or above can be tracked using radar. But both explosions would have generated millions of smaller fragments which are difficult to detect.

The space station has shields to protect it against objects under 1cm in size. Anything larger than 1cm would be perfectly capable of penetrating these shields.

In space, no one can hear you leak .. and have your frozen urine turn into a dollop of space debris capable of destroying space ordnance...