You've identified some significant safety issues with this temporary service setup. Here's a breakdown

Problems:
Floating Neutral/Ground Bus

This is a

major safety hazard. The neutral and ground need to be bonded together at the service. The fact that the bus bar is floating on a plastic spacer means there is no reliable path for fault current to return to the source. This can leave the enclosure, conduit, and anything connected to them energized during a fault. Missing Main Bonding Jumper (MBJ)

The MBJ is essential. It's the connection that bonds the neutral/ground bus to the metal enclosure.

Single Ground Rod

The NEC (National Electrical Code) generally requires two ground rods for a temporary service. There are exceptions, but they require testing the resistance to ground of a single rod to be 25 ohms or less, which is rarely the case.

Potential for Neutral Current on Conduit

This is a consequence of the missing MBJ. Without a proper bonding connection, fault current can potentially find its way back to the transformer via the metal conduit, which is not designed for this purpose and can be dangerous.

Why the Bus Bar is Floating (and why it's wrong)

It's hard to say for sure why someone installed it this way. Here are some possibilities, but

none of them are valid reasons to leave it as-is: Misunderstanding of Grounding

The person installing might have thought that keeping the neutral and ground "isolated" in the panel was somehow beneficial. This is incorrect and creates a dangerous situation.

Incorrect Parts

It's possible that the wrong bus bar or mounting hardware was used, and rather than correct it, the installer simply left it floating.

Ignorance

Unfortunately, some people simply don't understand the principles of grounding and bonding.

What Needs to be Done IMMEDIATELY


Do NOT Use This Service

It is unsafe and should not be energized until these issues are corrected.2.

Call a Qualified Electrician

This is not a DIY situation. You need a licensed electrician with experience in service installations to inspect and correct the wiring.3.

Correct Grounding and Bonding



Bond the Neutral/Ground Bus

The electrician will need to properly bond the neutral/ground bus to the metal enclosure. This likely involves removing the plastic spacer and directly bolting the bus bar to the enclosure. If the panel isn't designed for this, a suitable bonding jumper (wire) will need to be installed.

Install a Main Bonding Jumper

A properly sized MBJ must connect the neutral/ground bus to the enclosure.

Install a Second Ground Rod

If a single ground rod hasn't been tested and confirmed to be at or below 25 ohms to ground then a second ground rod will need to be installed at least 6 feet away from the first.4.

Inspect the Entire Installation

The electrician should thoroughly inspect the rest of the temporary service for other code violations or safety concerns.5.

Verify Proper Wiring

The electrician should use a meter to ensure that the grounding and bonding are correctly implemented and that there are no stray voltages on the enclosure.

Why This is So Important

Proper grounding and bonding are critical for electrical safety. They provide a low-impedance path for fault current to return to the source, causing the overcurrent protection device (circuit breaker or fuse) to trip quickly and safely de-energize the circuit. Without this, the enclosure of appliances and equipment can become energized during a fault, posing a risk of electric shock.

In Summary:

What you've described is a dangerous situation. Do not use this temporary service until a qualified electrician has corrected the grounding and bonding issues. Your safety and the safety of others depend on it. Flag for review