Lots of folks assume that the war destroyed civil and church records. However, until you hear it from the diocesan/state archives or from the parish or gmina office, don't assume that's true. While the records for a particular parish may have been destroyed, that doesn't mean that the civil copy of those records in the possession of the the state archives or local civil office or the copies sent to the diocese archives also were destroyed. Yes, there are records that were destroyed, but it's probably a lot less than folks assume. Priests went to great lengths to protect the sacramental records.
Because the records for Myszyniec were not filmed by the LDS doesn't mean that they don't exist. The LDS must obtain permission to film church registers, and the diocese may not have consented. Or they just haven't gotten to filming that set of parish records yet. I'd definitely recommend emailing the Lomza diocese and asking if the records exist. You can email in English, but your reply will be in Polish. The email address for the diocese can be found on their website. If the records should be located in the Plock diocese, they'll tell you so.
There are two other people researching in Myszyniec parish listed on this page:http://www.rootsweb.com/~polmazow/researchers.html
. Perhaps if you email them, they can confirm/deny that the records for this parish have been destroyed.
It's probably not worth your time to contact the church in Czarnia unless you're sure the records are there. Priests are pretty much the only person in the parish who can look up the info you want from their registers. It can take months, if not an entire year, to get a response. And some priests don't respond to genealogical queries at all.
Have you check the Ellis Island online database for passenger records? At a quick glance, I found a Katarzyna, Marianna, and Antonina Radek from Surowe (mother and children) arriving on 17 May 1903 at the port of New York. They are going to a brother, Valentine Radek, in Union City, CT. There's another Katharzina Radek from Surowe arriving in NY on 31 August 1903 and is going to her husband, Jozef Radek in Union City, CT. This Katharzina had been in Union City from 1900 to 1902. A Katharina Radek arrived at the port of NY on 18 March 1913 and was going to her uncle, Walenty Radek in Union City. She was born in Surowe and her father's name was Piotr (living in Surowe, Lomza, Russia).
A Jozef Radek from Sorowy arrived at NY port in 4 May 1899 and was going to an uncle (no name given) in Union City, CT. Another (or possibly the same) Jozef Radek born in Sarowo arrived on 20 November 1906 and was going to a brother Walenty Radek in Union City, CT. This Jozef had been in Union City between 1898-1903. A Stanislaw Radek born in Surowy arrived on 17 May 1905 and was going to his uncle, Walenty Radek, in Union City.