[SamBam]

I expect that many people pronounce "plover" as "clover" if they saw it written down first before they heard someone who knows the pronunciation say it. There are plenty of words like that in English.

I pronounced it as rhyming with "clover" too before learning that it's actually incorrect.

[wyattpeak]

That's possible too, though I don't subscribe to the idea that a widely used pronunciation can be incorrect.