I've put a shapefile with 47 features into a directory within a tar file. Ogrinfo reports 48 features. I'm also testing vsizip but don't see a problem there.
$ gdal-config --version
1.9.2
$ ogrinfo -so /vsitar/docs/data/test_uk.tar/testing/test_uk.shp test_uk
ERROR 4: Unable to open /vsitar/docs/data/test_uk.tar/testing/test_uk.shp or /vsitar/docs/data/test_uk.tar/testing/test_uk.SHP.
Had to open data source read-only.
INFO: Open of `/vsitar/docs/data/test_uk.tar/testing/test_uk.shp'
using driver `ESRI Shapefile' successful.
Layer name: test_uk
Geometry: 3D Polygon
Feature Count: 48
Extent: (-8.621389, 49.911659) - (1.749444, 60.844444)
Layer SRS WKT:
GEOGCS["GCS_WGS_1984",
DATUM["WGS_1984",
SPHEROID["WGS_84",6378137,298.257223563]],
PRIMEM["Greenwich",0],
UNIT["Degree",0.017453292519943295]]
CAT: Real (16.0)
FIPS_CNTRY: String (80.0)
CNTRY_NAME: String (80.0)
AREA: Real (15.2)
POP_CNTRY: Real (15.2)
I'm attaching the ogrinfo dump to show that it only contains 47 features.
ogrinfo dump