Upgraded this EE1 site to EE2 (not without issues but managed to get most of them fixed followed this [Upgrading an EE1 site to EE2 with nGen File field](https://expressionengine.stackexchange.com/questions/1/upgrading-an-ee1-site-to-ee2-with-ngen-file-field) as a guide but forgot 1 field). 
I'm stuck with 1 issue regarding 1 ngen file field that I forgot to convert to a text field. 

This ngen file field sits inside a matrix field in just 1 entry in 1 channel. 

I'm simply trying to delete this channel and its channel field group and recreate it without the ngen file field but I keep getting an error when I try to **access** the field:

```
    An Error Was Encountered 
Unable to load requested field type file: ft.ngen_file_field.php. 
Confirm the fieldtype file is located in the expressionengine/third_party/ directory

```

When I try to **delete** the field the error is:

```
A Database Error Occurred Error Number: 1091

Can't DROP 'col_id_15'; check that column/key exists

ALTER TABLE exp_matrix_data DROP col_id_15

Filename: third_party/matrix/ft.matrix.php

Line Number: 1544

```

Any suggestions on how to tackle this?