HMRC lock on VAT registration

Went into a client to see about filing an online VAT return for quarter ended 28 February 2014. No unsubmitted returns available. Went into submitted returns to check that it hadn't got filed already. It it had, it would have been an issue that needed rectifying as I had prepared the figures. Last return filed was for 30 November 2013 as expected. Telephoned up the HMRC VAT helpline. The VAT registration has been put on lock. Initially, the person on the phone told me this was because they had returned post from that address. As I knew the client was still at the address, and had been for some time I pressed on this point, hoping to at least narrow down a timescale to investigate. They admitted that this was the only reason they knew of for a lock, but they could not definitely say any letter had actually been returned.

To be clear, I only discovered this when accessing the online site for normal processing. I can understand stopping correspondence to an address if it appeared no longer valid. What I cannot understand is why we, as registered agent, were not informed of the issue. The filing of online returns is actually under our agent login, so it is not even a case that our authority was not clear.  How do they expect these things to get fixed if they just ignore it entirely? Does anyone know of any way to ensure we, as agents, are informed of these things?

As an aside, the lock on the account is what prevented the February return being "issued" (electronically, so issued seems rather a strong word). Though my phone call should have got the lock lifted, the system can no longer issue a February return. The next return for the client will therefore be a six month return to the end of May. I'm not advocating returning HMRC post to grant yourself an apparently penalty-free extension to a VAT deadline, but that seems like rather a gaping system hole to me.