I've just thought of another, similar-sounding verb that poses the same problem: 'rota'. Although the Concise OED lists 'rota' as a noun only ("Chiefly Brit. A list showing times and names for people to take their turn to undertake certain duties"), I have heard it used as a verb to mean something along the lines of 'to put into a rota'.
And no, I'm not imagining it: after quite some searching I managed to find a Personnel Today question-and-answer page in which a respondent ('BKay') writes:
Because we work a 7 day week if anyone is rotad to work a b/hol they get the day back in lieu
This writer has chosen 'rotad' as the past participle of 'rota' but I can see arguments for 'rotaed' or even 'rota'd'. What do you reckon?
And are there any other English verbs out there (apart from 'pro rata' and 'rota') whose spelling ends in a consonant and then the letter 'a'?