I doubt that's the case, but if it is then it shouldn't be. Children are abducted by parents without custody all the time. The warning signals would be a child travelling with only a father to an overseas destination that looks like it might be the father's place of heritage - especially if the destination is an Islamic country which would give custody of the child to an Islamic father. From the UK, that would typically be Pakistan, Bangladesh or the Middle East.

That doesn't mean that mothers don't abduct children or that it can't involve non-Islamic countries. For example, in Australia a mother can't emigrate with a child who has an Australian father without his consent (in fact, she can't even move interstate within Australia).