You are right. 'A lot' can be either singular or plural, depending on whether it refers to a singular or plural noun.
For example, 'Many small birds begin the flight across the ocean, but a lot GET lost on the way.'
Here 'a lot' means 'a lot of small birds', so the verb takes a plural form.
But in your example, 'A lot GETS lost in translation', you are right to use a singular verb. This is because 'a lot' probably refers to 'sense' , 'meaning', 'humour' or another uncountable noun.