I know this is a late reply but...

If cats are ill or distressed they will quite often pee in places they shouldn't as a way of attracting attention - when they do this they tend to do it anywhere and often in front of you. So be observant because a sudden change in behaviour could be a warning that something serious is wrong.

...just a tip - don't use any amonia based cleaning agents as this is a similar smell to cats urine and can encourage spraying - even amongst desexed cats.