Part Bodies hiding in an assembly

[Ronan1961]

I have 3 components of the same type that have mysteriously become hidden in an assembly. They are the curved strips in the screenshot. I can't make them show. it happened after I mirrored them. Hav since deleted the mirror. The only way I can get them to temporarily show up is to is to select in the path finder and use "Select related Faces". The part opens fine. If I drag in another copy of the part from path finder that is visible. The part also shows up if I select Edit Definition.
Any ideas on the cause of this? Obviously I can just delete and re -insert them.

[Ronan1961]

I partially found the cause of the problem. The curved strip is imported as a sheet metal part. Yet SE can't convert it to sheet metal apparently because there are no straight edges. The mass properties are 0. It should weigh about 12-20 grams. Do SE it sort of treating it as surfaces. In the assembly it initially shows ok but when mirrored it hides. I made it redisplay by show hide component -ticking surfaces. So that solves my direct problem.
As an aside
How would one convert this to sheet metal.
Can you get pattern recognise to pickup the 8 holes

Attached is the file in step 242 format as I am using the community version.

[KennyG]

Doesn't look like your STEP file has any geometry in it. Ran it through the NIST STEP Analyzer to confirm.

[Ronan1961]

Doesn't look like your STEP file has any geometry in it. Ran it through the NIST STEP Analyzer to confirm.

Thank you. mmm... Don't know what caused that. So I reimported the part from Sw. All is fine now.