I agree with @rbynaker  and it would help if you knew this was direct or indirect. If your client took possession of the funds in between, then put that into two different brokerages/accounts, you should expect one 1099-R to show the full distribution, but 1 or 2 5498 to show the money In.

Or, you likely have one 1099-R for the money out, into another traditional IRA. Then, that new Traditional IRA account manager will issue the 1099-R for the partial balance that got converted.

Keep watching for the mail.